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CVE Record

CVE-2026-42011: Gnutls: gnutls: security bypass due to incorrect name constraint handling

A flaw was found in gnutls. This vulnerability occurs because permitted name constraints were incorrectly ignored when previous Certificate Authorities (CAs) only had excluded name constraints. A remote attacker could exploit this to bypass critical name constraint checks during certificate validation. This bypass could lead to the acceptance of invalid certificates, potentially enabling spoofing or man-in-the-middle attacks against affected systems.

HighCVSS 7.4Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

GnuTLS may accept certificates it should reject when certificate authority name constraints are processed incorrectly. That can weaken trust decisions in TLS and may enable spoofing or man-in-the-middle scenarios. The issue is rated high, but the provided sources do not show known active exploitation.

Executive priority

Treat as a high-priority patching item for systems where TLS trust decisions protect sensitive traffic. It is not shown as exploited here, but successful abuse could undermine authentication and confidentiality.

Technical view

CVE-2026-42011 is a CWE-295 certificate validation flaw in GnuTLS. Permitted name constraints can be ignored when earlier CAs only contain excluded constraints, allowing bypass of critical constraint checks. Red Hat lists affected gnutls packages across RHEL 7 ELS, 8, 9, and 10, with libtasn1 also affected on several RHEL 8 streams.

Likely exposure

Exposure is most likely on Red Hat systems using the listed gnutls or libtasn1 packages, especially TLS clients or services that validate certificate chains from external networks, partners, proxies, or private PKI environments.

Exploitation context

The CVSS vector shows network attackability, no privileges, no user interaction, high confidentiality and integrity impact, and high attack complexity. KEV is false in the bundle, and no cited source here confirms active exploitation.

Researcher notes

Focus review on X.509 name constraint handling in GnuTLS chain validation, especially CA chains mixing excluded-only constraints before permitted constraints. Evidence is limited to the provided CVE, Red Hat, and GnuTLS references.

Mitigation direction

  • Apply the relevant Red Hat errata for each affected RHEL stream.
  • Update gnutls and libtasn1 packages where Red Hat marks them affected.
  • Check vendor guidance for fixed builds before using compensating controls.
  • Review containers and appliances that may bundle affected Red Hat packages.
  • Prioritize systems that validate certificates from untrusted or partner-controlled networks.

Validation and detection

  • Inventory installed gnutls and libtasn1 package versions across RHEL systems.
  • Map hosts to the affected RHEL products and package builds listed in the bundle.
  • Confirm vulnerability scanner results reference CVE-2026-42011 after package updates.
  • Validate TLS clients reject certificates outside permitted name constraints after remediation.
  • Review certificate validation failure logs for suspicious or unexpected chain behavior.
Prepared
Confidence
high
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-295: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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description · low confidence lookup

Container behavior lookup

The affected technology mentions containers, so container-specific ATT&CK technique review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2026-42011 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.4 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
5Timeline events
1ADP providers
19Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.4CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N2.25.2redhat

Vulnerability scoring details

Base CVSS 3.1 score

7.4High
CVSS 3.1 vector shape for CVE-2026-42011Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. Source timelineredhat

    Made public.

  3. Source timelineredhat

    Reported to Red Hat.

  4. CVE publishedCVE Program

    The CVE record was published.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Red HatRed Hat Enterprise Linux 10gnutls, 0:3.8.10-4.el10_2affected
Red HatRed Hat Enterprise Linux 10.0 Extended Update Supportgnutls, 0:3.8.9-9.el10_0.19affected
Red HatRed Hat Enterprise Linux 7 Extended Lifecycle Supportgnutls, 0:3.3.29-9.el7_9.2affected
Red HatRed Hat Enterprise Linux 8gnutls, 0:3.6.16-8.el8_10.6affected
Red HatRed Hat Enterprise Linux 8gnutls, 0:3.6.16-8.el8_10.6affected
Red HatRed Hat Enterprise Linux 8.4 Advanced Mission Critical Update Supportgnutls, 0:3.6.14-10.el8_4.1affected
Red HatRed Hat Enterprise Linux 8.4 Advanced Mission Critical Update Supportlibtasn1, 0:4.13-3.el8_4.1affected
Red HatRed Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-Ongnutls, 0:3.6.14-10.el8_4.1affected
Red HatRed Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-Onlibtasn1, 0:4.13-3.el8_4.1affected
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Supportgnutls, 0:3.6.16-5.el8_6.5affected
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Supportlibtasn1, 0:4.13-3.el8_6.2affected
Red HatRed Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-Ongnutls, 0:3.6.16-5.el8_6.5affected
Red HatRed Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-Onlibtasn1, 0:4.13-3.el8_6.2affected
Red HatRed Hat Enterprise Linux 8.8 Telecommunications Update Servicegnutls, 0:3.6.16-7.el8_8.4affected
Red HatRed Hat Enterprise Linux 8.8 Telecommunications Update Servicelibtasn1, 0:4.13-4.el8_8.1affected
Red HatRed Hat Enterprise Linux 8.8 Update Services for SAP Solutionsgnutls, 0:3.6.16-7.el8_8.4affected
Red HatRed Hat Enterprise Linux 8.8 Update Services for SAP Solutionslibtasn1, 0:4.13-4.el8_8.1affected
Red HatRed Hat Enterprise Linux 9gnutls, 0:3.8.10-4.el9_8affected
Red HatRed Hat Enterprise Linux 9gnutls, 0:3.8.10-4.el9_8affected
Red HatRed Hat Enterprise Linux 9.2 Update Services for SAP Solutionsgnutls, 0:3.7.6-21.el9_2.7affected
Red HatRed Hat Enterprise Linux 9.4 Update Services for SAP Solutionsgnutls, 0:3.8.3-4.el9_4.6affected
Red HatRed Hat Enterprise Linux 9.6 Extended Update Supportgnutls, 0:3.8.3-6.el9_6.4affected
Red HatRed Hat OpenShift Container Platform 4.19rhcos, 4.19.9.6.202607151909-0affected
Red HatRed Hat Discovery 2discovery/discovery-server-rhel9, 1782159791affected
Red HatRed Hat Discovery 2discovery/discovery-ui-rhel9, 1782166952affected
Red HatRed Hat Hardened Imagesgnutls-main, 3.8.13-1.hum1affected
Red HatRed Hat Update Infrastructure 5rhui5/cds-rhel9, 1781525684affected
Red HatRed Hat Update Infrastructure 5rhui5/haproxy-rhel9, 1781525671affected
Red HatRed Hat Update Infrastructure 5rhui5/installer-rhel9, 1781525693affected
Red HatRed Hat Update Infrastructure 5rhui5/rhua-rhel9, 1781525739affected
Weakness

CWE details

CWE-295

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-295 · source CWE mapping

Improper Certificate Validation

Improper Certificate Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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