CVE-2026-85008

undici vulnerable to caching and replay of unsafe HTTP method responses

Workarounds

None.

undici's interceptors.cache() documents that it caches only safe HTTP methods. However, its internal skip-list is built by subtracting the configured methods from the safe-methods set, so an unsafe method (POST, PUT, PATCH, DELETE) never lands in the skip-list and is looked up against the cache store. Combined with the storage gate (canCacheResponse) having no method check, a heuristically-cacheable response (for example a 404) with an explicit Cache-Control: max-age=... to an unsafe method is stored and replayed on a subsequent identical request. The application's state-changing request never reaches the origin, and undici serves a fabricated response from the cache instead. This occurs with the default configuration (methods: ['GET']), which the public API does not allow widening to unsafe methods, so no application misuse is required; an untrusted origin can trigger it purely through its own response headers.

CVE-2026-85008 has a CVSS score of 3.7 (Low). The vector is network-reachable, no 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 (7.29.1, 8.10.2); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

Upgrade to 7.29.1 or 8.10.2. The cache interceptor no longer reads from or writes to the cache for unsafe HTTP methods, while still invalidating existing cache entries on successful unsafe requests.

1. What is CVE-2026-85008? CVE-2026-85008 is a low-severity security vulnerability in undici (npm), affecting versions >= 7.0.0, < 7.29.1. It is fixed in 7.29.1, 8.10.2.
2. How severe is CVE-2026-85008? CVE-2026-85008 has a CVSS score of 3.7 (Low). 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 undici are affected by CVE-2026-85008? undici (npm) versions >= 7.0.0, < 7.29.1 is affected.
4. Is there a fix for CVE-2026-85008? Yes. CVE-2026-85008 is fixed in 7.29.1, 8.10.2. Upgrade to this version or later.
5. Is CVE-2026-85008 exploitable, and should I be worried? Whether CVE-2026-85008 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-2026-85008 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-2026-85008?
   • Upgrade undici to 7.29.1 or later
   • Upgrade undici to 8.10.2 or later

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