# CVE-2026-27586: caddy: Caddy is an extensible server platform that uses TLS by default

CVE-2026-27586 is fixed in 4 products on 1 platform, first by DEBIAN-CVE-2026-27586, released February 24, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-27586
- Priority: Urgent
- CVSS: 9.1 (critical)
- EPSS: 0.0030
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Feb 24, 2026

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | caddy Debian 14 | 2.11.2-1 | [DEBIAN-CVE-2026-27586](https://patchblox.com/security/data/fix/linux/debian-cve-2026-27586.md) | Feb 24, 2026 |
| Linux | caddy Fedora 43 | 2.10.2-9.fc43 | [FEDORA-2026-3DC324BD9A](https://patchblox.com/security/data/fix/linux/fedora-2026-3dc324bd9a.md) | Jun 23, 2026 |
| Linux | caddy-debuginfo Fedora 43 | 2.10.2-9.fc43 | [FEDORA-2026-3DC324BD9A](https://patchblox.com/security/data/fix/linux/fedora-2026-3dc324bd9a.md) | Jun 23, 2026 |
| Linux | caddy-debugsource Fedora 43 | 2.10.2-9.fc43 | [FEDORA-2026-3DC324BD9A](https://patchblox.com/security/data/fix/linux/fedora-2026-3dc324bd9a.md) | Jun 23, 2026 |
| Linux | govulncheck-vulndb opensuse-leap 15.6 | 0.0.20260226T182644-150000.1.149.1 | [SUSE-SU-2026:0757-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-0757-1.md) | Mar 3, 2026 |
| Linux | govulncheck-vulndb opensuse-leap 16.0 | 0.0.20260723T184607-160000.1.1 | [OPENSUSE-SU-2026:21483-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21483-1.md) | Jul 30, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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