CVE-2026-15074

@fastify/static up to and including version 10.1.0 fails to reject dot-dot path segments in request pathnames before the file-resolution stage. This is a bypass of the earlier fix for CVE-2026-6414, which only covered encoded forward slashes. Because the underlying send library normalizes dot segments before applying its own path-traversal guard, an unauthenticated attacker can bypass any route-scoped middleware and read files inside the static root that live under the guarded URL prefix. The bypass does not allow access outside the configured static root by itself, it defeats route-guard filtering only. The issue is patched in @fastify/static 10.1.1.

@fastify/static up to and including version 10.1.0 fails to reject dot-dot path segments in request pathnames before the file-resolution stage. This is a bypass of the earlier fix for CVE-2026-6414, which only covered encoded forward slashes. Because the underlying send library normalizes dot segments before applying its own path-traversal guard, an unauthenticated attacker can bypass any route-scoped middleware and read files inside the static root that live under the guarded URL prefix. The bypass does not allow access outside the configured static root by itself, it defeats route-guard filtering only. The issue is patched in @fastify/static 10.1.1.

Impact

@fastify/static is vulnerable to a bypass of route-based middleware and guards via non-leading .. and %2E%2E path segments. find-my-way does not normalize .. when matching routes, so a request such as /foo/../deep/secret.txt matches the static plugin's catch-all instead of the guarded /deep/*. The getPathnameForSend helper introduced by the fix for GHSA-x428-ghpx-8j92 only guards against the %2F variant; .. and %2E%2E survive the decodeURI + encodeURI round-trip and are then collapsed away by @fastify/send's path.normalize before its own traversal guard runs.

Applications that rely on route-based middleware or guards to protect files served by @fastify/static can be bypassed with non-leading dot-dot path segments.

Patches

Upgrade to @fastify/static 10.1.1.

Workarounds

Do not use route-based middlewares or guards to protect files served by @fastify/static.

@fastify/static up to and including version 10.1.0 fails to reject dot-dot path segments in request pathnames before the file-resolution stage. This is a bypass of the earlier fix for CVE-2026-6414, which only covered encoded forward slashes. Because the underlying send library normalizes dot segments before applying its own path-traversal guard, an unauthenticated attacker can bypass any route-scoped middleware and read files inside the static root that live under the guarded URL prefix. The bypass does not allow access outside the configured static root by itself, it defeats route-guard filtering only. The issue is patched in @fastify/static 10.1.1.

@fastify/static up to and including version 10.1.0 fails to reject dot-dot path segments in request pathnames before the file-resolution stage. This is a bypass of the earlier fix for CVE-2026-6414, which only covered encoded forward slashes. Because the underlying send library normalizes dot segments before applying its own path-traversal guard, an unauthenticated attacker can bypass any route-scoped middleware and read files inside the static root that live under the guarded URL prefix. The bypass does not allow access outside the configured static root by itself, it defeats route-guard filtering only. The issue is patched in @fastify/static 10.1.1.

Impact

@fastify/static is vulnerable to a bypass of route-based middleware and guards via non-leading .. and %2E%2E path segments. find-my-way does not normalize .. when matching routes, so a request such as /foo/../deep/secret.txt matches the static plugin's catch-all instead of the guarded /deep/*. The getPathnameForSend helper introduced by the fix for GHSA-x428-ghpx-8j92 only guards against the %2F variant; .. and %2E%2E survive the decodeURI + encodeURI round-trip and are then collapsed away by @fastify/send's path.normalize before its own traversal guard runs.

Applications that rely on route-based middleware or guards to protect files served by @fastify/static can be bypassed with non-leading dot-dot path segments.

Patches

Upgrade to @fastify/static 10.1.1.

Workarounds

Do not use route-based middlewares or guards to protect files served by @fastify/static.