CVE-2026-27588 HIGH

CVE-2026-27588: Caddy: MatchHost becomes case-sensitive for large host lists (>100), enabling host-based route/auth bypass

Vendor Caddyserver
Product caddy
Weakness CWE-178
Published February 24, 2026
Last update February 27, 2026
View on NVD All CVEs

CVSS base score

7.7/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS vector

CVSS: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

What the vulnerability does

01Description

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's HTTP `host` request matcher is documented as case-insensitive, but when configured with a large host list (>100 entries) it becomes case-sensitive due to an optimized matching path. An attacker can bypass host-based routing and any access controls attached to that route by changing the casing of the `Host` header. Version 2.11.1 contains a fix for the issue.

Key dates

02Disclosure timeline

February 24, 2026 CVE published
February 27, 2026 Record updated