# CVE-2026-95210: GnuTLS improper certificate validation in extension processing

Source: https://junglewise.ai/threats/cve-2026-95210-improper-certificate-validation-in-gnutls-v3-8-13-causes-the  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-08. Updated: 2026-10-19  
License: CC BY 4.0 with a link back

CVE-2026-95210 · Severity: medium · CVSS 4.8 · Published 2026-10-08

GnuTLS is a cryptographic library used to validate SSL/TLS certificates in applications. A flaw in version 3.8.13 allows it to accept certificates with malformed critical extensions that should be rejected, creating a situation where validation succeeds but later use of the certificate fails. An attacker can exploit this by providing a crafted certificate that GnuTLS marks as trusted but that contains invalid data, potentially bypassing security policy checks.

Technologies: [GnuTLS](https://junglewise.ai/threats/technologies/gnutls-gnutls). Vendors: [GnuTLS](https://junglewise.ai/threats/vendors/gnutls).

## Quick answers

**Is CVE-2026-95210 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-95210 being exploited in the wild.

**How severe is CVE-2026-95210?** Medium severity, with a CVSS score of 4.8, published 8 October 2026.

**Which products and versions are affected?** GnuTLS 3.8.13.

**Is there a fix for CVE-2026-95210?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-95210 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-95210?** Check whether you run GnuTLS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

GnuTLS's path validation performs a critical-extension check using only OID matching (is_ext_oid_supported()) without parsing the extension value itself. When an end-entity certificate carries a critical keyUsage extension with a malformed value (e.g., DER-encoded NULL instead of BIT STRING), the validation gate passes because the OID is recognized. However, the actual extension value is never parsed during verification, only during lazy accessor calls that may never occur on the end-entity certificate. This creates a gap where gnutls_x509_ext_import_key_usage() would reject the malformed value but is never invoked, violating RFC 5280's requirement to reject critical extensions that cannot be processed.

## Affected products

- GnuTLS GnuTLS 3.8.13

## Timeline

- 2026-10-08: disclosed

## References

- [http://gnutls.com/](http://gnutls.com/)
- [https://gist.github.com/lkloliver/4aad23689202720c4068f43b3c6069c7](https://gist.github.com/lkloliver/4aad23689202720c4068f43b3c6069c7)

## Related threats

- [GnuTLS certificate validation denial of service](https://junglewise.ai/threats/cve-2026-95209-an-issue-in-gnutls-v3-8-13-causes-legitimate-ca-certificates-to)
- [GnuTLS improper X.509 certificate validation](https://junglewise.ai/threats/cve-2026-67693-an-issue-in-gnutls-v-3-8-13-allows-an-attacker-to-obtain)