CVE-2026-52844: Caddy: Windows `file_server` path authorization bypass via encoded backslash

June 16, 2026 (updated July 20, 2026)

On Windows, Caddy path matchers treat /private\secret.txt as outside /private/*, but file_server later resolves the same request path as private\secret.txt on disk.

An unauthenticated remote client can request /private%5csecret.txt and bypass Caddy path-scoped auth/deny routes protecting /private/*.

References

github.com/advisories/GHSA-qrp7-cvwr-j2c6
github.com/caddyserver/caddy/security/advisories/GHSA-qrp7-cvwr-j2c6
nvd.nist.gov/vuln/detail/CVE-2026-52844

Code Behaviors & Features

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