CVE-2026-27586
Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, two swallowed errors in `ClientAuthentication.provision()` cause mTLS client certificate authentication to silently fail open when a CA certificate file is missing, unreadable, or malformed. The server starts without error but accepts any client certificate signed by any system-trusted CA, completely bypassing the intended private CA trust boundary. Any deployment using `trusted_ca_cert_file` or `trusted_ca_certs_pem_files` for mTLS will silently degrade to accepting any system-trusted client certificate if the CA file becomes unavailable. This can happen due to a typo in the path, file rotation, corruption, or permission changes. The server gives no indication that mTLS is misconfigured. Version 2.11.1 fixes the vulnerability.
- Affected products
- Caddy
- Caddyserver Caddy
- < 2.11.1
- Fix
- Available
- CVSS 4.0
- 9.3 CRITICAL
- CVSS 3.1
- 9.1 CRITICAL
- EPSS
- 0.3% (19th percentile)
- Weakness
- CWE-755
- NVD status
- Analyzed
- Published
- 2026-02-24
No indexed exploits for CVE-2026-27586 yet
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No exploit for CVE-2026-27586 has been indexed yet. Our index is built from live traffic and upstream syncs, so this page can only say what it knows — not that no exploit exists.