CVE-2026-27587: Caddy: MatchPath %xx (escaped-path) branch skips case normalization, enabling path-based route/auth bypass

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-02-24 · updated 2026-06-17
Weakness: CWE-178

Description

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 products

caddyserver caddy: from 2.10.2 before 2.11.1 — fixed in 2.11.1

How to fix

Upgrade to a fixed version: caddyserver caddy 2.11.1. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2026-27587 or the next vulnerability affects your stack