by Kastro
Paper/Archive/CVE-2026-27587

CVE-2026-27587

caddyserver caddy — Caddy: MatchPath %xx (escaped-path) branch skips case normalization, enabling path-based route/auth bypass

EPSS 0.4%public exploitCVSS 9.1
critical.is priorityof 100
45
CVSS 9.1 (NVD)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 36.8.368 × 207.4Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's HTTP `path` request matcher is intended to be case-insensitive, but when the match pattern contains percent-escape sequences (`%xx`) it compares against the request's escaped path without lowercasing. An attacker can bypass path-based routing and any access controls attached to that route by changing the casing of the request path. Version 2.11.1 contains a fix for the issue.

Affected

ProductAffectedFixed inSource
caddy< 2.11.1–CNA

Scores by source

NVD9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
GitHub_M (CNA)7.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
CISA ADPSSVCExploitation: poc · Automatable: yes · Technical impact: partial

References

refgithub.com/caddyserver/caddy/security/advisories/GHSA-g7pc-pc7g-h8jhrefgithub.com/caddyserver/caddy/releases/tag/v2.11.1