Echo static file middleware route protection bypass via encoded dot-dot traversal

Summary Echo v5.2.0 contains a bypass of the fix for GHSA-vfp3-v2gw-7wfq. The fix rejects encoded path separators such as %2F and %5C before static file path unescaping, but two traversal forms still bypass route-level middleware protections for static files. The primary bypass uses encoded dot-dot segments. A request such as /public/%2E%2E/admin/secret.txt passes the encoded-separator guard, is unescaped to public/../admin/secret.txt, then path.Clean resolves it to admin/secret.txt. If /admin/ is protected by middleware but the static filesystem is mounted at /, the protected file is returned through the public static route. A second bypass exists when UseEscapedPathForMatching=true. In that mode, the router normalizes encoded separators before the static handler checks the wildcard. The handler receives a decoded wildcard with no % characters, so the encoded-separator guard does not run on the original encoded path. Impact An unauthenticated attacker can read files that an application intended to protect with route-level middleware, when those files are also reachable through a static filesystem mount after path normalization. The high-severity variant works with the default…

curl https://cve.zerocrew.in/api/cve/CVE-2026-118654