Vulnerability Details 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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 8.2%
CVSS Severity
CVSS v3 Score 7.5
References
Products affected by CVE-2026-30852
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cpe:2.3:a:caddyserver:caddy:2.10.0
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cpe:2.3:a:caddyserver:caddy:2.10.1
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cpe:2.3:a:caddyserver:caddy:2.10.2
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cpe:2.3:a:caddyserver:caddy:2.11.0
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cpe:2.3:a:caddyserver:caddy:2.11.1
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cpe:2.3:a:caddyserver:caddy:2.7.5
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cpe:2.3:a:caddyserver:caddy:2.7.6
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cpe:2.3:a:caddyserver:caddy:2.8.0
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cpe:2.3:a:caddyserver:caddy:2.8.1
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cpe:2.3:a:caddyserver:caddy:2.8.2
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cpe:2.3:a:caddyserver:caddy:2.8.3
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cpe:2.3:a:caddyserver:caddy:2.8.4
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cpe:2.3:a:caddyserver:caddy:2.9.0
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cpe:2.3:a:caddyserver:caddy:2.9.1