CVE-2026-30852CWE-200CWE-74

Caddy: vars_regexp double-expands user input, leaking env vars and files

Medium · published March 7, 2026

CVSS v4.0
5.5
EPSS
1%
Percentile
42.3
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
5.5 · MEDIUM
Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P
EPSS
0.00505 · 42.3th percentile
Weaknesses
CWE-200 · Exposure of Sensitive Information to an Unauthorized Actor; CWE-74 · Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
Published
2026-03-07T16:28Z
EPSS history
Timeline
  • 07 MAR 16:28Z
    Caddy: vars_regexp double-expands user input, leaking env vars and files
    cvelistv5