CVE-2026-52845
Description
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
github.com/caddyserver/caddy/v2Go | < 2.11.4 | 2.11.4 |
github.com/caddyserver/caddyGo | <= 1.0.5 | — |
Affected products
3cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:*+ 1 more
- cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:*range: <2.11.4
- (no CPE)range: <= 1.0.5
- osv-coordsRange: < 0.0.20260727T201416-160000.1.1
Patches
Vulnerability mechanics
References
6- github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45gnvdExploitThird Party AdvisoryWEB
- github.com/advisories/GHSA-f59h-q822-g45gghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-52845ghsaADVISORY
- access.redhat.com/security/cve/CVE-2026-52845nvdWEB
- bugzilla.redhat.com/show_bug.cginvdWEB
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52845.jsonnvdWEB
News mentions
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