CVE-2026-33308Public exploitNetwork attack vector

Authentication bypass via unchecked certificate key purpose

Published Mar 24, 2026 · Updated Mar 24, 2026

Improper certificate validation in mod_gnutls before 0.13.0 allows remote attackers to bypass TLS client authentication using a valid certificate. The client-certificate verification path accepts a CA-trusted certificate without checking whether its Extended Key Usage permits client authentication. Exploitation requires the matching private key, client-certificate verification enabled, and a certificate from a broadly trusted CA; default configurations that ignore client certificates are unaffected.

CVSS severity6.8
Medium
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in mod_gnutls before 0.13.0 allows remote attackers to bypass TLS client authentication using a valid certificate. The client-certificate verification path accepts a CA-trusted certificate without checking whether its Extended Key Usage permits client authentication. Exploitation requires the matching private key, client-certificate verification enabled, and a certificate from a broadly trusted CA; default configurations that ignore client certificates are unaffected.

The record

CVE
CVE-2026-33308
Published
Mar 24, 2026
Updated
Mar 24, 2026
Vendor
airtower-luna
Product
mod_gnutls
Classifications
CWE-295, T1649
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.13.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

airtower-luna · mod_gnutlsversion=< 0.13.0

Published CVSS scores

5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
6.8GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1649Steal or Forge Authentication Certificates

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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