PatchSiren cyber security CVE debrief
CVE-2026-42011 Red Hat CVE debrief
A vulnerability in GnuTLS allows remote attackers to bypass certificate name constraint validation when previous Certificate Authorities (CAs) only had excluded name constraints. The flaw causes permitted name constraints to be incorrectly ignored in this specific chain configuration, potentially enabling certificate spoofing or man-in-the-middle attacks. The vulnerability carries a HIGH severity CVSS 3.1 score of 7.4. Red Hat has issued security advisories addressing this issue.
- Vendor
- Red Hat
- Product
- Red Hat Enterprise Linux 8
- CVSS
- HIGH 7.4
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-05-07
- Original CVE updated
- 2026-05-27
- Advisory published
- 2026-05-07
- Advisory updated
- 2026-05-27
Who should care
Organizations running services that rely on GnuTLS for TLS certificate validation, particularly those using custom or complex certificate authority hierarchies with name constraints. System administrators maintaining Red Hat Enterprise Linux systems with GnuTLS dependencies. Security teams responsible for certificate infrastructure and TLS security posture. Application developers embedding GnuTLS for cryptographic operations.
Technical summary
The vulnerability exists in GnuTLS certificate chain validation logic. When processing a certificate chain where previous CAs have only excluded name constraints (rather than permitted name constraints), the implementation incorrectly ignores subsequent permitted name constraints. This logic error allows an attacker to craft a certificate chain that bypasses intended name restriction policies. The attack requires network access to the target system and high attack complexity, with no user interaction needed. Successful exploitation results in acceptance of invalid certificates, compromising confidentiality and integrity of TLS connections.
Defensive priority
high
Recommended defensive actions
- Apply security updates from Red Hat as provided in RHSA-2026:13274 and RHSA-2026:20611
- Review TLS certificate validation configurations in applications using GnuTLS
- Monitor certificate chain validation logs for anomalous behavior
- Validate that certificate pinning mechanisms are in place for critical services
- Assess exposure of GnuTLS-dependent services to untrusted network paths
Evidence notes
Vulnerability description sourced from NVD official record. Red Hat errata RHSA-2026:13274 and RHSA-2026:20611 provide vendor confirmation and remediation. Bugzilla entry 2467437 tracks the issue. CVSS vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N indicates network attack vector with high attack complexity, no privileges required, no user interaction, and high impact to confidentiality and integrity.
Official resources
2026-05-07