CVE-2026-55434

Coder vulnerable to denial of service via unbounded request body in AI Bridge provider endpoints

AI Bridge provider handlers read request bodies with io.ReadAll without a maximum size so an authenticated user with AI Bridge access could send an arbitrarily large body and exhaust memory.

Note: Exploitation requires authenticated access to the AI Bridge endpoints and the impact is limited to availability (denial of service).

Workarounds

None.

Resources

• Fix: #26164

Credits

Coder would like to thank Anthropic's Security Team (ANT-2026-22443) for independently disclosing this issue!

An authenticated member-level user could POST a very large or chunked body to an AI Bridge provider endpoint such as /api/v2/aibridge/anthropic/v1/messages, growing heap memory until the operating system terminates the process. Because AI Bridge runs in-process with coderd, this crashes the entire control plane, including the API, workspace coordinator and DERP relay. It requires an authenticated user and the AI Bridge feature enabled.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

CVE-2026-55434 has a CVSS score of 6.5 (Medium). The vector is network-reachable, low privileges required, and no user interaction. 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); upgrading removes the vulnerable code path.

Kodem intelligence

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The fix applies http.MaxBytesReader or an equivalent cap before reading provider and session request bodies. The affected AI Bridge provider endpoints exist only on the v2.33 and v2.34 lines. Earlier release lines are not affected.

The fix is available in the following releases:

1. What is CVE-2026-55434? CVE-2026-55434 is a medium-severity allocation of resources without limits or throttling 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. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is CVE-2026-55434? CVE-2026-55434 has a CVSS score of 6.5 (Medium). 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-2026-55434? github.com/coder/coder/v2 (go) versions >= 2.34.0, < 2.34.2 is affected.
4. Is there a fix for CVE-2026-55434? Yes. CVE-2026-55434 is fixed in 2.34.2, 2.33.8. Upgrade to this version or later.
5. Is CVE-2026-55434 exploitable, and should I be worried? Whether CVE-2026-55434 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-2026-55434 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-2026-55434?
   • Upgrade github.com/coder/coder/v2 to 2.34.2 or later
   • Upgrade github.com/coder/coder/v2 to 2.33.8 or later

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