CVE-2026-52845
Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, forward_auth copy_headers deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through php_fastcgi, Caddy normalizes HTTP headers into CGI variables by replacing - with _. This lets a client send an underscore alias that survives the forward_auth delete step but becomes the same PHP/FastCGI variable. Result: a remote client can inject or sometimes override identity/group headers trusted by PHP/FastCGI applications behind Caddy. This vulnerability is fixed in 2.11.4.
- CVSS 3.1
- 8.1
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N - EPSS
- 0.4% chance of exploitation in the next 30 days; higher than 38% of CVEs (scores of 2026-10-25)
- CWEs
- CWE-287, CWE-290, CWE-444
- Published
- Modified
- Record from
- the NVD, synced
Affected
- caddyserver:caddy
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-f59h-q822-g45g | Go | github.com/caddyserver/caddy/v2 | <2.11.4 | 2.11.4 |
| GHSA-f59h-q822-g45g | Go | github.com/caddyserver/caddy | <=1.0.5 | no fix published |
| GO-2026-5346 | Go | github.com/caddyserver/caddy/v2 | <2.11.4 | 2.11.4 |
References
- https://github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45g
- https://access.redhat.com/security/cve/CVE-2026-52845
- https://bugzilla.redhat.com/show_bug.cgi?id=2491907
- https://github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45g
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52845.json