Atlassian Finds Public Exploit for Critical Bug

Atlassian Confluence Server and Data Center contain an unauthenticated remote code execution flaw caused by improper neutralization of expression-language (OGNL) input (CWE-917): an attacker with network access to the application can submit a crafted request that is evaluated as an expression and executed by the server. Successful exploitation lets a remote, unauthenticated attacker run arbitrary code with the privileges of the Confluence process, without any credentials. All organizations running self-managed Confluence Server or Data Center are affected, particularly instances exposed to the internet; Confluence Cloud is not listed among the affected products. Exploitation is confirmed in the wild: the flaw was added to CISA's KEV on 2022-06-02 with ransomware use marked as known, and EPSS assigns a 100% probability of exploitation within 30 days (100th percentile). CVSS has not yet been scored in this data, but the KEV listing and known ransomware use make unpatched, internet-facing instances a top-priority patching target.

Do: Immediately upgrade to the patched Confluence release specified in Atlassian's 2022-06-02 security advisory, and until patched follow the CISA required action to block all internet traffic to and from affected instances. Because in-the-wild exploitation and ransomware use are confirmed, also hunt for compromise indicators on both patched and unpatched hosts, such as webshells, unexpected child processes of the Confluence service, and unusual outbound connections.

Atlassian Confluence Data Center and Server contain a broken access control flaw (CWE-20) in publicly accessible instances that allows unauthenticated remote attackers to create unauthorized Confluence administrator accounts and gain access to the instance; the associated public PoC is titled 'Atlassian Confluence Unauthenticated Remote Code Execution'. The flaw is triggered over the network (CVSS 3.1 9.8, AV:N/AC:L/PR:N/UI:N) against any self-managed Confluence instance reachable from the internet, with no privileges or user interaction required. Attackers who exploit it gain administrator-level control of the Confluence instance, and the public PoC demonstrates this extends to unauthenticated code execution. Only self-managed Confluence Data Center and Server deployments are affected; Atlassian Cloud sites hosted on atlassian.net domains are not vulnerable. Exploitation is confirmed in the wild: CISA added it to the KEV on 2023-10-05 with known ransomware use, EPSS is 99.2%, Atlassian reported a handful of customers were already exploited, and Microsoft warned of nation-state (China-linked) abuse.

Do: Patch all internet-facing Confluence Data Center and Server instances to a fixed release per Atlassian's advisory (specific fixed versions are not listed in this data), or restrict public access/discontinue use per CISA's required action. Audit every affected instance for evidence of compromise, especially unauthorized administrator accounts created through this flaw, and report positive findings to CISA. Treat this as urgent given active exploitation by both nation-state actors and ransomware groups.

Atlassian Confluence Data Center and Server contain an improper authorization flaw (CWE-863) that can be triggered by an unauthenticated attacker sending crafted requests to a vulnerable instance. Successful exploitation gives the attacker control over the instance and can cause significant data loss, such as wiping or resetting the Confluence site, but there is no confidentiality impact because no data can be exfiltrated. Any organization running a self-managed Confluence Data Center or Server deployment is in scope. Exploitation is active: the flaw was added to CISA's Known Exploited Vulnerabilities catalog on 2023-11-07 with ransomware use noted, and EPSS assigns it a 100% probability of exploitation within 30 days. No public proof-of-concept is known, but ransomware operators are already using the flaw in the wild.

Do: Upgrade every Confluence Data Center and Server instance to the patched release for your branch listed in Atlassian's advisory, per the CISA KEV required action (apply vendor mitigations or discontinue use). In the interim, restrict internet access to Confluence and check for signs of compromise such as unexpected instance resets, missing data, or ransom notes; restore from backups if data loss is detected.