CVE-2026-30852
HIGH
GHSA-m2w3-8f23-hxxf
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Lifecycle Timeline
4Description
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.
Analysis
Caddy versions 2.7.5 through 2.11.1 contain a template injection vulnerability in the vars_regexp matcher that allows remote attackers to perform double variable expansion on user-controlled input, enabling disclosure of environment variables and file contents. By injecting placeholders like {env.DATABASE_URL} or {file./etc/passwd} into request headers, an unauthenticated attacker can leak sensitive system information. …
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Remediation
Within 24 hours: Identify all Caddy deployments and document current versions. Within 7 days: Test and deploy Caddy 2.11.2 or later in a controlled environment. …
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External POC / Exploit Code
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