CVE-2026-27588
Critical
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.
SeverityCritical
CVSS9.1
Exploit probability—
Product
Caddy
PublishedFeb 24, 2026
First seenFeb 24, 2026
Weakness typeCWE-178CWE-178
How to fix
Update
- caddyserver caddy2.11.1 or later
- github.com/caddyserver/caddy/v22.11.1 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| caddyserver caddy | 2.10.2 ≤ v < 2.11.1 | 2.11.1 |
| github.com/caddyserver/caddy/v2Go | v < 2.11.1 | 2.11.1 |
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