CVE-2025-47269

code-server prior to version 4.99.4 fails to properly validate the port portion of URLs passed to its built-in /proxy subpath, allowing a crafted URL to proxy traffic to an arbitrary attacker-controlled domain (CWE-441, unspecified proxy-related issue). If a user running code-server with the built-in proxy enabled clicks a malicious link such as https://their-server/proxy/[email protected]/path, the connection is forwarded to the attacker's domain, with cookies included. The attacker can then capture the user's session token, log into the victim's code-server instance, and gain full access to the hosting machine as the user running code-server (CVSS 3.1: 8.3 high; network vector, requires user interaction, high confidentiality and integrity impact). All users self-hosting code-server versions before 4.99.4 with the built-in proxy enabled are affected. There is no confirmed in-the-wild exploitation, no public PoC, and it is not listed in CISA KEV, but the high EPSS score of 42.7% (99th percentile) indicates a substantial probability of exploitation within 30 days.

What to do: Upgrade code-server to version 4.99.4 or later. As interim mitigation, disable the built-in proxy feature or restrict network egress from code-server hosts, and avoid clicking links to /proxy paths on code-server instances from untrusted sources. Check code-server access logs for /proxy requests containing '@' in the path (arbitrary-host patterns) and invalidate/rotate session cookies if any are found.