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Improper Certificate ValidationWeakness · CWE-295

CVE-2026-42011

HIGH · 7.4 CVSS v3.1 Published 2026-05-07
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
83/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A flaw was found in gnutls. This vulnerability occurs because permitted name constraints were incorrectly ignored when previous Certificate Authorities (CAs) only had excluded name constraints. A remote attacker could exploit this to bypass critical name constraint checks during certificate validation. This bypass could lead to the acceptance of invalid certificates, potentially enabling spoofing or man-in-the-middle attacks against affected systems.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A flaw in GnuTLS causes permitted name constraints to be incorrectly ignored when previous Certificate Authorities (CAs) only had excluded name constraints, allowing invalid certificates to pass validation checks.

MitigationUpdate GnuTLS to the latest patched version. In the meantime, verify certificate chains carefully and consider using additional validation layers.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm GnuTLS is present
    Check for GnuTLS library files: look for libgnutls* in /usr/lib or /usr/lib64, or run 'dpkg -l | grep gnutls' (Debian) / 'rpm -qa | grep gnutls' (RHEL)
    Affected if GnuTLS library is not installed on the system
  2. Identify installed GnuTLS version
    Run 'gnutls-cli --version' or 'gnutls-serv --version' for command-line tools; for the library, check '/usr/lib64/libgnutls.so.*' or use 'pkg-config --modversion gnutls'
    Affected if Unable to determine version or version is prior to the patched release containing the fix for name constraint validation
  3. Verify the system performs TLS certificate validation
    Review application configurations or service files that use GnuTLS for TLS (check for 'tls' or 'ssl' in config files, or grep for gnutls-linked binaries with 'ldd /path/to/binary | grep gnutls')
    Affected if No applications or services use GnuTLS for TLS/SSL connections
  4. Check if name constraint validation is in use
    Examine CA certificate chains or TLS configurations that involve Certificate Authorities with defined name constraints (examine .pem or .crt CA bundle files for 'nameConstraints' extension)
    Affected if Certificate validation does not involve CAs with name constraints defined in the chain

The system is affected if GnuTLS is installed, the version lacks the name constraint fix, and the environment performs X.509 certificate validation using CA certificates that include name constraint extensions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update GnuTLS to the latest patched version. In the meantime, verify certificate chains carefully and consider using additional validation layers.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,800
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-42011 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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