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Vulnerability Details :

CVE-2026-27586

Summary
Assigner-GitHub_M
Assigner Org ID-a0819718-46f1-4df5-94e2-005712e83aaa
Published At-24 Feb, 2026 | 16:08
Updated At-24 Feb, 2026 | 16:08
Rejected At-
Credits

Caddy's mTLS client authentication silently fails open when CA certificate file is missing or malformed

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.

Vendors
-
Not available
Products
-
Metrics (CVSS)
VersionBase scoreBase severityVector
Weaknesses
Attack Patterns
Solution/Workaround
References
HyperlinkResource Type
EPSS History
Score
Latest Score
-
N/A
No data available for selected date range
Percentile
Latest Percentile
-
N/A
No data available for selected date range
Stakeholder-Specific Vulnerability Categorization (SSVC)
▼Common Vulnerabilities and Exposures (CVE)
cve.org
Assigner:GitHub_M
Assigner Org ID:a0819718-46f1-4df5-94e2-005712e83aaa
Published At:24 Feb, 2026 | 16:08
Updated At:24 Feb, 2026 | 16:08
Rejected At:
▼CVE Numbering Authority (CNA)
Caddy's mTLS client authentication silently fails open when CA certificate file is missing or malformed

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
Vendor
caddyserver
Product
caddy
Versions
Affected
  • < 2.11.1
Problem Types
TypeCWE IDDescription
CWECWE-755CWE-755: Improper Handling of Exceptional Conditions
Type: CWE
CWE ID: CWE-755
Description: CWE-755: Improper Handling of Exceptional Conditions
Metrics
VersionBase scoreBase severityVector
4.08.8HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
Version: 4.0
Base score: 8.8
Base severity: HIGH
Vector:
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
https://github.com/caddyserver/caddy/security/advisories/GHSA-hffm-g8v7-wrv7
x_refsource_CONFIRM
https://gist.github.com/moscowchill/9566c79c76c0b64c57f8bd0716f97c48
x_refsource_MISC
https://github.com/caddyserver/caddy/releases/tag/v2.11.1
x_refsource_MISC
Hyperlink: https://github.com/caddyserver/caddy/security/advisories/GHSA-hffm-g8v7-wrv7
Resource:
x_refsource_CONFIRM
Hyperlink: https://gist.github.com/moscowchill/9566c79c76c0b64c57f8bd0716f97c48
Resource:
x_refsource_MISC
Hyperlink: https://github.com/caddyserver/caddy/releases/tag/v2.11.1
Resource:
x_refsource_MISC
Information is not available yet
▼National Vulnerability Database (NVD)
nvd.nist.gov
Source:security-advisories@github.com
Published At:24 Feb, 2026 | 17:29
Updated At:24 Feb, 2026 | 21:52

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.

CISA Catalog
Date AddedDue DateVulnerability NameRequired Action
N/A
Date Added: N/A
Due Date: N/A
Vulnerability Name: N/A
Required Action: N/A
Metrics
TypeVersionBase scoreBase severityVector
Secondary4.08.8HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Type: Secondary
Version: 4.0
Base score: 8.8
Base severity: HIGH
Vector:
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CPE Matches
Weaknesses
CWE IDTypeSource
CWE-755Primarysecurity-advisories@github.com
CWE ID: CWE-755
Type: Primary
Source: security-advisories@github.com
Evaluator Description
Evaluator Impact

Evaluator Solution

Vendor Statements
References
HyperlinkSourceResource
https://gist.github.com/moscowchill/9566c79c76c0b64c57f8bd0716f97c48security-advisories@github.com
N/A
https://github.com/caddyserver/caddy/releases/tag/v2.11.1security-advisories@github.com
N/A
https://github.com/caddyserver/caddy/security/advisories/GHSA-hffm-g8v7-wrv7security-advisories@github.com
N/A
Hyperlink: https://gist.github.com/moscowchill/9566c79c76c0b64c57f8bd0716f97c48
Source: security-advisories@github.com
Resource: N/A
Hyperlink: https://github.com/caddyserver/caddy/releases/tag/v2.11.1
Source: security-advisories@github.com
Resource: N/A
Hyperlink: https://github.com/caddyserver/caddy/security/advisories/GHSA-hffm-g8v7-wrv7
Source: security-advisories@github.com
Resource: N/A

Change History

0
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