Vulnerabilities

CVE-2026-18730 is a server-side request forgery (CWE-918) in the Manage API of GitHub Enterprise Server (GHES) that lets an unauthenticated attacker cause the instance to send crafted outbound requests to an attacker-controlled host. The flaw stems from an unauthenticated endpoint that parses an attacker-supplied cluster configuration and issues gateway-to-agent requests whose HMAC token authenticates only a timestamp, not the request path or body, so an attacker positioned to intercept the outbound request can capture the token. By replaying the captured token against privileged management agent endpoints, the attacker gains unauthorized access to management functionality, with the primary impact being disclosure of confidential management information (CVSS v4 rates confidentiality impact High, with no integrity or availability impact). All GHES versions prior to 3.22 are affected; fixes are available in 3.17.19, 3.18.13, 3.19.10, 3.20.6, and 3.21.4, and high-availability deployments are explicitly not affected due to a topology restriction. No public proof of concept, no CISA KEV listing, and a low EPSS score (0.3%, 23rd percentile) indicate no known exploitation at this time.

Do: Upgrade GitHub Enterprise Server to 3.17.19, 3.18.13, 3.19.10, 3.20.6, or 3.21.4 (or any 3.22+ release). Audit whether your deployment runs the affected non-HA/clustered topology, whether the unauthenticated Manage API endpoint is reachable, and whether management agent tokens should be rotated if instances could have been observed. High-availability deployments are not affected and need no action under this advisory.

A path traversal vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to delete arbitrary files and directories on the instance, including the entire user storage directory containing Git LFS objects, release assets, attachments, and avatars. The X-GitHub-Request-Id request header was used without sanitization as a filesystem path segment for the upload buffer directory, so a traversal value pointed the buffer at an arbitrary path and the deferred cleanup routine recursively removed the traversed target. Exploitation required only network reachability to the instance and no authentication, and it worked even when private mode was enabled. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.21.4, 3.20.6, 3.19.10, 3.18.13 and 3.17.19. This vulnerability was reported via the GitHub Bug Bounty program.

GitHub MCP Server versions prior to 1.1.0 contain a nil pointer dereference (CWE-476) in the CompletionsHandler function in pkg/github/server.go, which accesses the ref field of a completion request without first verifying it is present. Any unauthenticated client able to send JSON-RPC messages to the server can trigger the flaw by issuing a completion/complete request with a missing or empty ref field. Because the dereference happens before any authentication or token validation, the resulting Go runtime panic crashes the server and yields a complete denial of service. All deployments running an affected version are potentially affected, with the greatest risk for instances reachable over a network by unauthenticated clients, while locally run stdio instances are only reachable by their local client. No widespread exploitation is reported (0.4% EPSS, not in CISA KEV), but a public security advisory documents the issue and the triggering request is trivial to craft.

Do: Upgrade to GitHub MCP Server 1.1.0 or later, which adds the missing nil check in CompletionsHandler. Until patched, restrict any HTTP/SSE-exposed instance with authentication or network allowlisting, since the crashing request requires no credentials. Audit deployments to determine which are network-reachable versus local-only, and watch for unauthenticated completion/complete requests that crash the process.

An incorrect authorization vulnerability was identified in GitHub Enterprise Server that allowed a user-to-server token scoped to a GitHub App installation to perform certain write operations on public repositories outside the token's intended scope. This was possible because the authorization check only verified that the installation had read permissions on the target repository rather than verifying that the token's installation was explicitly granted access to that repository. An attacker who obtained a victim's user-to-server token could create issues, issue comments, commit comments, and private vulnerability reports on any public repository, appearing as the victim user with no indication of the app involvement. This vulnerability was fixed by adding a repository scope check for user-to-server tokens issued by global apps. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.21.2, 3.20.4, 3.19.8, 3.18.11, 3.17.17, 3.16.20. This vulnerability was reported via the GitHub Bug Bounty program.

A stored cross-site scripting vulnerability was identified in GitHub Enterprise Server that allowed an authenticated attacker to execute arbitrary JavaScript in another user's browser by injecting a crafted payload into the title of a Discussion in the Q&A category. The AnsweredQuestionStructuredDataComponent did not escape user-controlled Discussion titles before embedding them in a block, allowing the title to break out of the script context. The injection was escalated to a full cross-site scripting attack on GitHub Enterprise Server by leveraging JSONP callback support in the REST API to bypass the Content Security Policy. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.4, 3.19.8, 3.18.11, 3.17.17, 3.16.20. This vulnerability was reported via the GitHub Bug Bounty program.

GitHub CLI (gh) is GitHub’s official command line tool. Prior to 2.93.0, GitHub CLI incorrectly includes authorization header in API requests to TUF repository mirrors via gh attestation, gh release verify, and gh release verify-asset commands. The CLI uses a shared HTTP client with an authentication layer that automatically attaches tokens to outgoing requests. This layer lacks accurate host detection and can incorrectly attribute the target host, providing it with a token it should never receive. Specifically, the host normalization logic collapses any *.github.com subdomain to github.com, so a request to tuf-repo.github.com (a GitHub Pages site, not a GitHub API endpoint) is treated as a request to github.com and receives the user's github.com token. For hosts that don't match github.com or a known GHES instance at all, the resolver falls back to GH_ENTERPRISE_TOKEN if set. The gh attestation, gh release verify and gh release verify-asset commands fetch data from several external hosts as part of their normal operation (TUF metadata from tuf-repo.github.com and tuf-repo-cdn.sigstore.dev, artifact bundles from Azure Blob Storage). Because these requests go through the same authenticated HTTP client, the token is sent to all of them. This vulnerability is fixed in 2.93.0.

A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to send crafted requests to internal services by exploiting insufficient input validation in an upload endpoint. By injecting path traversal content into request parameters, an attacker could bypass the intended request flow and redirect internal API calls, potentially accessing internal services and exposing sensitive credentials. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.17.17, 3.18.11, 3.19.8, 3.20.4, and 3.21.2. This vulnerability was reported via the GitHub Bug Bounty program.

`gh` is GitHub’s official command line tool. From 1.6.0 to before 2.92.0, a security vulnerability has been identified in GitHub CLI that could allow terminal escape sequence injection when users view GitHub Actions workflow logs using gh run view --log or gh run view --log-failed. The vulnerability stems from the way GitHub CLI handles raw Actions log output. The gh run view --log and gh run view --log-failed commands stream workflow log lines to stdout or the configured pager without sanitizing terminal control sequences. An attacker who can influence GitHub Actions log content, for example via a PR triggered workflow, can embed escape sequences that are replayed in the user's terminal when they inspect the run. Depending on the victim's terminal emulator, injected sequences could change the window title, manipulate on screen content, or in some terminal emulators (such as screen) potentially execute arbitrary commands. This vulnerability is fixed in 2.92.0.

GitHub Copilot CLI brings AI-powered coding assistance directly to your command line. Prior to 1.0.43, a security vulnerability has been identified in GitHub Copilot CLI where a malicious bare git repository nested inside a project directory can achieve arbitrary code execution when the agent performs git operations. By exploiting git's automatic bare repository discovery during directory traversal, an attacker can set core.fsmonitor or other executable config keys to run arbitrary commands without user awareness or approval. The vulnerability arises because git's core.fsmonitor config key (and 15+ similar keys such as core.hookspath, diff.external, merge.tool, etc.) can specify arbitrary shell commands that git will execute as part of normal operations like status, diff, or rev-parse. This vulnerability is fixed in 1.0.43.

A server-side request forgery (SSRF) vulnerability was identified in the GitHub Enterprise Server notebook viewer that allowed an attacker to access internal services by exploiting URL parser confusion between the validation layer and the HTTP request library. The hostname validation used a different URL parser than the request library, enabling a crafted URL to pass validation while directing the request to an unintended host. Exploitation required network access to the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.16.18, 3.17.15, 3.18.9, 3.19.6, and 3.20.2. This vulnerability was reported via the GitHub Bug Bounty program.

A server-side request forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an attacker to extract sensitive environment variables from the instance through a timing side-channel attack against the notebook rendering service. When private mode was disabled, the notebook viewer followed HTTP redirects without revalidating the destination host, enabling an unauthenticated SSRF to internal services. By chaining this with regex filter queries against an internal API and measuring response time differences, an attacker could infer secret values character by character. Exploitation required that private mode be disabled and that the attacker be able to chain the instance's open redirect endpoint through an external redirect to reach internal services. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.14.26, 3.15.21, 3.16.17, 3.17.14, 3.18.8, 3.19.5, and 3.20.1. This vulnerability was reported via the GitHub Bug Bounty program.

CVE-2026-3854 is an improper neutralization flaw (CWE-77) in GitHub Enterprise Server in which user-supplied git push option values are placed into internal service headers without sanitization. An authenticated user with push access to any repository can trigger it with a single crafted git push, injecting additional metadata fields through the delimiter character used in the internal header format. Successful injection yields remote code execution on the GHES instance, giving the attacker control of the server and the code repositories it hosts. All self-hosted GHES deployments running affected builds in the 3.14 through 3.19 branches are affected; fixes are available in 3.14.25, 3.15.20, 3.16.16, 3.17.13, 3.18.7 and 3.19.4. No public proof-of-concept or confirmed in-the-wild exploitation is known yet, but the 40% EPSS score (99th percentile) indicates a high probability of exploitation within 30 days, and the flaw is not yet in CISA's KEV catalog.

Do: Upgrade GitHub Enterprise Server to 3.14.25, 3.15.20, 3.16.16, 3.17.13, 3.18.7 or 3.19.4 (or later in each branch) as a priority, given the 40% EPSS likelihood of near-term exploitation. If patching must wait, review and restrict push-access grants to trusted users and consider disabling git push options (receive.advertisePushOptions=false) since they are the injection vector. Check GHES upgrade and push-related logs for anomalous activity from accounts with push access.

The shell tool within GitHub Copilot CLI versions prior to and including 0.0.422 can allow arbitrary code execution through crafted bash parameter expansion patterns. An attacker who can influence the commands executed by the agent (e.g., via prompt injection through repository files, MCP server responses, or user instructions) can exploit bash parameter transformation operators to execute hidden commands, bypassing the safety assessment that classifies commands as "read-only." This has been patched in version 0.0.423. The vulnerability stems from how the CLI's shell safety assessment evaluates commands before execution. The safety layer parses and classifies shell commands as either read-only (safe) or write-capable (requires user approval). However, several bash parameter expansion features can embed executable code within arguments to otherwise read-only commands, causing them to appear safe while actually performing arbitrary operations. The specific dangerous patterns are ${var@P}, ${var=value} / ${var:=value}, ${!var}, and nested $(cmd) or <(cmd) inside ${...} expansions. An attacker who can influence command text sent to the shell tool - for example, through prompt injection via malicious repository content (README files, code comments, issue bodies), compromised or malicious MCP server responses, or crafted user instructions containing obfuscated commands - could achieve arbitrary code execution on the user's workstation. This is possible even in permission modes that require user approval for write operations, since the commands can appear to use only read-only utilities to ultimately trigger write operations. Successful exploitation could lead to data exfiltration, file modification, or further system compromise.

An URL redirection vulnerability was identified in GitHub Enterprise Server that allowed attacker-controlled redirects to leak sensitive authorization tokens. The repository_pages API insecurely followed HTTP redirects when fetching artifact URLs, preserving the authorization header containing a privileged JWT. An authenticated user could redirect these requests to an attacker-controlled domain, exfiltrate the Actions.ManageOrgs JWT, and leverage it for potential remote code execution. Attackers would require access to the target GitHub Enterprise Server instance and the ability to exploit a legacy redirect to an attacker-controlled domain. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.19 and was fixed in versions 3.19.2, 3.18.4, 3.17.10, 3.16.13, 3.15.17, and 3.14.22. This vulnerability was reported via the GitHub Bug Bounty program.

An Improper Neutralization of Input During Web Page Generation vulnerability was identified in GitHub Enterprise Server that allowed attacker controlled HTML to be rendered by the Filter component (search) across GitHub that could be used to exfiltrate sensitive information. An attacker would require permissions to create or modify the names of milestones, issues, pull requests, or similar entities that are rendered in the vulnerable filter/search components. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.20 and was fixed in versions 3.19.1, and 3.18.2, 3.17.8, 3.16.11, 3.15.15, and 3.14.20. This vulnerability was reported via the GitHub Bug Bounty program.

An improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allowed user-supplied HTML to inject DOM elements with IDs that collided with server-initialized data islands. These collisions could overwrite or shadow critical application state objects used by certain Project views, leading to unintended server-side POST requests or other unauthorized backend interactions. Successful exploitation requires an attacker to have access to the target GitHub Enterprise Server instance and to entice a privileged user to view crafted malicious content that includes conflicting HTML elements. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.18.3, 3.17.9, 3.16.12, 3.15.16, and 3.14.21.

An improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allows DOM-based cross-site scripting via Issues search label filter that could lead to privilege escalation and unauthorized workflow triggers. Successful exploitation requires an attacker to have access to the target GitHub Enterprise Server instance and to entice a user, while operating in sudo mode, to click on a crafted malicious link to perform actions that require elevated privileges. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.18.1, 3.17.7, 3.16.10, 3.15.14, 3.14.19.

An improper access control vulnerability was identified in GitHub Enterprise Server that allowed users with access to any repository to retrieve limited code content from another repository by creating a diff between the repositories. To exploit this vulnerability, an attacker needed to know the name of a private repository along with its branches, tags, or commit SHAs that they could use to trigger compare/diff functionality and retrieve limited code without proper authorization. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.18, and was fixed in versions 3.14.17, 3.15.12, 3.16.8 and 3.17.5. This vulnerability was reported via the GitHub Bug Bounty program.

An incorrect authorization vulnerability allowed unauthorized read access to the contents of internal repositories for contractor accounts when the Contractors API feature was enabled. The Contractors API is a rarely-enabled feature in private preview. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.18 and was fixed in versions 3.14.15, 3.15.10, 3.16.6 and 3.17.3

An exposure of sensitive information vulnerability was identified in GitHub Enterprise Server that could allow an attacker to disclose the names of private repositories within an organization. This issue could be exploited by leveraging a user-to-server token with no scopes via the Search API endpoint. Successful exploitation required an organization administrator to install a malicious GitHub App in the organization’s repositories. This vulnerability impacted only GitHub Enterprise Server version 3.17 and was addressed in version 3.17.2. The vulnerability was reported through the GitHub Bug Bounty program.

An improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allowed cross-site scripting in GitHub Markdown that used `$$..$$` math blocks. Exploitation required access to the target GitHub Enterprise Server instance and privileged user interaction with the malicious elements. This vulnerability affected version 3.16.1 of GitHub Enterprise Server and was fixed in version 3.16.2. This vulnerability was reported via the GitHub Bug Bounty program.

A Code Injection vulnerability was identified in GitHub Enterprise Server that allowed attackers to inject malicious code into the query selector via the identity property in the message handling function. This enabled the exfiltration of sensitive data by manipulating the DOM, including authentication tokens. To execute the attack, the victim must be logged into GitHub and interact with the attacker controlled malicious webpage containing the hidden iframe. This vulnerability occurs due to an improper sequence of validation, where the origin check occurs after accepting the user-controlled identity property. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.11.16, 3.12.10, 3.13.5, 3.14.2, and 3.15.0. This vulnerability was reported via the GitHub Bug Bounty program.

An improper verification of cryptographic signature vulnerability was identified in GitHub Enterprise Server that allowed signature spoofing for unauthorized internal users. Instances not utilizing SAML single sign-on or where the attacker is not already an existing user were not impacted. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.12.14, 3.13.10, 3.14.7, 3.15.2, and 3.16.0. This vulnerability was reported via the GitHub Bug Bounty program.

The GitHub CLI version 2.6.1 and earlier are vulnerable to remote code execution through a malicious codespace SSH server when using `gh codespace ssh` or `gh codespace logs` commands. This has been patched in the cli v2.62.0. Developers connect to remote codespaces through an SSH server running within the devcontainer, which is generally provided through the [default devcontainer image]( https://docs.github.com/en/codespaces/setting-up-your-project-for-codespaces/adding-a-dev-container-... https://docs.github.com/en/codespaces/setting-up-your-project-for-codespaces/adding-a-dev-container-configuration/introduction-to-dev-containers#using-the-default-dev-container-configuration) . GitHub CLI [retrieves SSH connection details]( https://github.com/cli/cli/blob/30066b0042d0c5928d959e288144300cb28196c9/internal/codespaces/rpc/inv... https://github.com/cli/cli/blob/30066b0042d0c5928d959e288144300cb28196c9/internal/codespaces/rpc/invoker.go#L230-L244 ), such as remote username, which is used in [executing `ssh` commands]( https://github.com/cli/cli/blob/e356c69a6f0125cfaac782c35acf77314f18908d/pkg/cmd/codespace/ssh.go#L2... https://github.com/cli/cli/blob/e356c69a6f0125cfaac782c35acf77314f18908d/pkg/cmd/codespace/ssh.go#L263 ) for `gh codespace ssh` or `gh codespace logs` commands. This exploit occurs when a malicious third-party devcontainer contains a modified SSH server that injects `ssh` arguments within the SSH connection details. `gh codespace ssh` and `gh codespace logs` commands could execute arbitrary code on the user's workstation if the remote username contains something like `-oProxyCommand="echo hacked" #`. The `-oProxyCommand` flag causes `ssh` to execute the provided command while `#` shell comment causes any other `ssh` arguments to be ignored. In `2.62.0`, the remote username information is being validated before being used.

A path collision and arbitrary code execution vulnerability was identified in GitHub Enterprise Server that allowed container escape to escalate to root via ghe-firejail path. Exploitation of this vulnerability requires Enterprise Administrator access to the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise prior to 3.15 and was fixed in versions 3.14.3, 3.13.6, 3.12.11, and 3.11.17. This vulnerability was reported via the GitHub Bug Bounty program.

An information disclosure vulnerability was identified in GitHub Enterprise Server via attacker uploaded asset URL allowing the attacker to retrieve metadata information of a user who clicks on the URL and further exploit it to create a convincing phishing page. This required the attacker to upload malicious SVG files and phish a victim user to click on that uploaded asset URL. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.14 and was fixed in versions 3.14.2, 3.13.5, 3.12.10, 3.11.16. This vulnerability was reported via the GitHub Bug Bounty program.

CVE-2024-9487 is an improper verification of cryptographic signature flaw (CWE-347) in GitHub Enterprise Server that allows SAML SSO authentication to be bypassed. Exploitation requires the encrypted assertions feature to be enabled, direct network access to the instance, and a signed SAML response or metadata document supplied by the attacker. A successful attack results in unauthorized provisioning of users and unauthorized access to the instance. All GitHub Enterprise Server versions prior to 3.15 are affected, with fixes shipped in 3.11.16, 3.12.10, 3.13.5, and 3.14.2. No public proof-of-concept or confirmed in-the-wild exploitation is known yet, but EPSS assigns a 25.6% probability of exploitation within 30 days (98th percentile), indicating elevated risk.

Do: Upgrade GitHub Enterprise Server to version 3.14.2, 3.13.5, 3.12.10, or 3.11.16 (or any 3.15+ release). Administrators who cannot patch immediately should verify whether SAML SSO with encrypted assertions is enabled, limit direct network access to the instance, and review user provisioning logs for unexpected accounts. This flaw was reported via the GitHub Bug Bounty program and is not yet in CISA KEV.