Vulnerability Description
Caddy is an extensible server platform that uses TLS by default. From version 2.7.5 to before version 2.11.2, the vars_regexp matcher in vars.go:337 double-expands user-controlled input through the Caddy replacer. When vars_regexp matches against a placeholder like {http.request.header.X-Input}, the header value gets resolved once (expected), then passed through repl.ReplaceAll() again (the bug). This means an attacker can put {env.DATABASE_URL} or {file./etc/passwd} in a request header and the server will evaluate it, leaking environment variables, file contents, and system info. This issue has been patched in version 2.11.2.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Caddyserver | Caddy | >= 2.7.5, < 2.11.2 |
Related Weaknesses (CWE)
References
- https://github.com/caddyserver/caddy/pull/5408Issue TrackingPatch
- https://github.com/caddyserver/caddy/releases/tag/v2.11.2ProductRelease Notes
- https://github.com/caddyserver/caddy/security/advisories/GHSA-m2w3-8f23-hxxfExploitMitigationVendor Advisory
FAQ
What is CVE-2026-30852?
CVE-2026-30852 is a vulnerability with a CVSS score of 7.5 (HIGH). Caddy is an extensible server platform that uses TLS by default. From version 2.7.5 to before version 2.11.2, the vars_regexp matcher in vars.go:337 double-expands user-controlled input through the Ca...
How severe is CVE-2026-30852?
CVE-2026-30852 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-30852?
Check the references section above for vendor advisories and patch information. Affected products include: Caddyserver Caddy.