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Vulnerabilities

Vulnerability · CVE-2026-33307

Mod_gnutls is a TLS module for Apache HTTPD based on GnuTLS.

Published Mar 24, 2026 · catalog updated Jun 17, 2026 · mod gnutls project mod gnutls

Check if you run it

No confirmed exploitation is on record for CVE-2026-33307. EPSS is 0.31%. Act only if a listed version of mod gnutls project mod gnutls is installed.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.31%
Remediation
Advisory link
Affected products
cpe mod gnutls project/mod gnutls

Mod_gnutls is a TLS module for Apache HTTPD based on GnuTLS. In versions prior to 0.12.3 and 0.13.0, code for client certificate verification imported the certificate chain sent by the client into a fixed size array without checking the number of certificates is less than or equal to the array size. is a for a pointer to an opaque GnuTLS structure created using with before importing certificate data into it, so no attacker-controlled data was written into the stack buffer, but writing a pointer after the last array element generally triggered a segfault, and could theoretically cause stack corruption otherwise (not observed in practice). Server configurations that do not use client certificates ( , the default) are not affected. The problem has been fixed in version 0.12.3 by checking the length of the provided certificate chain and rejecting it if it exceeds the buffer length, and in version 0.13.0 by rewriting certificate verification to use , removing the need for the buffer entirely. There is no workaround. Version 0.12.3 provides the minimal fix for users of 0.12.x who do not wish to upgrade to 0.13.0 yet.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe mod gnutls project/mod gnutlsversion unspecified

How to fix CVE-2026-33307

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-33307. EPSS is 0.31%. Act only if a listed version of mod gnutls project mod gnutls is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-121: Stack-based Buffer Overflow. EPSS 0.31%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 24, 2026 · NIST NVD

    Detected

    Mod_gnutls is a TLS module for Apache HTTPD based on GnuTLS. In versions prior to 0.12.3 and 0.13.0, code for client certificate verification imported the certificate chain sent by the client into a fixed size array without checking the number of certificates is less than or equal to the array size. is a for a pointer to an opaque GnuTLS structure created using with before importing certificate da

  2. Jun 17, 2026 · NIST NVD

    Updated

    Mod_gnutls is a TLS module for Apache HTTPD based on GnuTLS. In versions prior to 0.12.3 and 0.13.0, code for client certificate verification imported the certificate chain sent by the client into a fixed size array without checking the number of certificates is less than or equal to the array size. is a for a pointer to an opaque GnuTLS structure created using with before importing certificate da

Sources

  • CVE.orgVulnerability recordCVE-2026-33307

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-33307

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-2026-33307

    Mod_gnutls is a TLS module for Apache HTTPD based on GnuTLS. In versions prior to 0.12.3 and 0.13.0, code for client certificate verification imported the certificate chain sent by the client into a fixed size array without checking the number of certif

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.