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CVE Record

CVE-2026-3833: Gnutls: gnutls: policy bypass due to case-sensitive nameconstraints comparison

A flaw was found in gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons of `nameConstraints` labels, specifically for `dNSName` (DNS) or `rfc822Name` (email) constraints within `excludedSubtrees` or `permittedSubtrees`. A remote attacker can exploit this by crafting a leaf certificate with casing differences in the Subject Alternative Name (SAN), leading to a policy bypass where a certificate that should be rejected is instead accepted. This could result in unauthorized access or information disclosure.

MediumCVSS 6.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

GnuTLS may accept a certificate that should be blocked by certificate name constraints because it compares DNS and email labels case-sensitively. The business risk is trust boundary failure in systems that depend on constrained CAs for TLS identity checks, potentially enabling unauthorized access or information disclosure.

Executive priority

Treat as a scheduled security update with targeted urgency for environments using constrained certificate authorities. It is not currently supported as an emergency active-exploitation issue, but it affects authentication trust decisions and should not be deferred indefinitely.

Technical view

CVE-2026-3833 is a CWE-178 case-sensitivity flaw in GnuTLS nameConstraints handling for dNSName and rfc822Name entries in excludedSubtrees or permittedSubtrees. A leaf certificate with case differences in SAN values may bypass policy checks. CVSS is 6.5, network exploitable, no privileges or user interaction required.

Likely exposure

Exposure is most likely on affected Red Hat Enterprise Linux systems using GnuTLS for certificate validation, especially RHEL 7 ELS, 8 support streams, 9, and 10. Some RHEL 8 streams also list libtasn1 packages. Non-Red Hat exposure is not established by the provided bundle.

Exploitation context

The bundle does not show CISA KEV listing or other evidence of active exploitation. Exploitation requires a certificate-validation path using GnuTLS name constraints and a certificate whose SAN differs by case from constrained DNS or email labels.

Researcher notes

Focus analysis on GnuTLS nameConstraints comparison semantics for dNSName and rfc822Name. The source bundle identifies the flaw and affected Red Hat package streams but does not include exploit proof, complete upstream fix details, or non-Red Hat affected-version evidence.

Mitigation direction

  • Apply the relevant Red Hat errata updates for affected RHEL streams.
  • Check Red Hat CVE guidance for fixed package versions before deployment.
  • Prioritize systems relying on constrained CAs or strict certificate policy enforcement.
  • Assess dependent services that link to GnuTLS for TLS certificate validation.
  • Use compensating controls where patching is delayed and certificate constraints are security-critical.

Validation and detection

  • Inventory RHEL hosts with affected gnutls or listed libtasn1 package versions.
  • Map services that use GnuTLS for certificate chain validation.
  • Confirm whether constrained CA trust paths are used for DNS or email names.
  • Verify Red Hat errata packages are installed after maintenance.
  • Review certificate validation logs for rejected or unexpected constrained-chain behavior.
Prepared
Confidence
medium
Sources
12

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-178: 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-2026-3833 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
Medium
CVSS
6.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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
18Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical Impact: partial

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
6.5CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N3.92.5redhat

Vulnerability scoring details

Base CVSS 3.1 score

6.5Medium
CVSS 3.1 vector shape for CVE-2026-3833Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

    Reported to Red Hat.

  3. Source timelineredhat

    Made public.

  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
Unknown vendorgnutlsgnutls, 0unaffected
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 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-178

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

CWE-178 · source CWE mapping

Improper Handling of Case Sensitivity

Improper Handling of Case Sensitivity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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