Improper Neutralization of Special Elements used in an Expression Language Statement in Caddy - #VU165957
Published: November 12, 2026
Vulnerability identifier: #VU165957
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-917
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to disclose environment variables, system information, and file contents up to 1 MB.
The vulnerability exists due to expression language injection in Caddy's variable matchers when header-derived values stored under literal variable keys undergo a second placeholder expansion. A remote attacker can send headers containing {env.AWS_SECRET_ACCESS_KEY} or {file./etc/passwd} to expose expanded secrets through configured response headers or forwarding to a backend.
Affected software
Caddy
Remediation
Install security update from vendor's website.
Caddy - update to 2.11.3