Vulnerability Description
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.
CVSS Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Caddyserver | Caddy | >= 2.10.2, < 2.11.1 |
Related Weaknesses (CWE)
References
- https://github.com/caddyserver/caddy/releases/tag/v2.11.1Release Notes
- https://github.com/caddyserver/caddy/security/advisories/GHSA-x76f-jf84-rqj8ExploitVendor Advisory
FAQ
What is CVE-2026-27588?
CVE-2026-27588 is a vulnerability with a CVSS score of 9.1 (CRITICAL). 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 l...
How severe is CVE-2026-27588?
CVE-2026-27588 has been rated CRITICAL with a CVSS base score of 9.1/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-27588?
Check the references section above for vendor advisories and patch information. Affected products include: Caddyserver Caddy.