Information disclosure in Caddyserver Caddy
CVE-2026-30852
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.005 (41.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 42nd percentile — 41.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.001
Affected products
- Caddyserver Caddy — versions >= 2.7.5, < 2.11.2
Weakness classification (CWE)
References
- github.com/caddyserver/caddy/security/advisories/GHSA-m2w3-8f23-hxxf (Exploit, Mitigation, Vendor Advisory)
- github.com/caddyserver/caddy/pull/5408 (Patch, Issue Tracking)
- github.com/caddyserver/caddy/releases/tag/v2.11.2 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-30852?
- CVE-2026-30852 is a high-severity vulnerability in Caddyserver Caddy, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 7.5/10. Published 2026-03-07.
- How severe is CVE-2026-30852?
- High severity. CVSS v3 base score is 7.5 out of 10.