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Vulnerability Assessment

Weakness
CWE
CWE-178
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Case sensitivity handling
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv3 – Jun 24, 2026

Certificate name-constraints bypass in GnuTLS allows a remote attacker to craft a leaf certificate whose Subject Alternative Name differs only in letter casing from a constrained dNSName or rfc822Name, causing GnuTLS to accept a certificate that its excludedSubtrees/permittedSubtrees policy should reject. The flaw stems from case-sensitive comparison of name-constraint labels and enables unauthorized access, impersonation, or information disclosure across software (notably Red Hat Enterprise Linux 6-10 and OpenShift Container Platform 4) that relies on GnuTLS for X.509 validation. SSVC notes a public proof-of-concept exists, though EPSS exploitation probability is very low (0.03%, 9th percentile) and the issue is not in CISA KEV.

Earlier versions of this analysis (2)
v2 Jun 24, 2026 - 17:33 cvss changed CVSS 7.4

Certificate name-constraints bypass in GnuTLS allows a remote attacker to defeat dNSName and rfc822Name restrictions by exploiting case-sensitive comparison (CWE-178) of nameConstraints labels in permittedSubtrees/excludedSubtrees. An attacker who crafts a leaf certificate whose Subject Alternative Name differs only in letter casing can have a certificate that should be rejected accepted as valid, enabling impersonation, unauthorized access, or information disclosure. SSVC indicates a proof-of-concept exists and the attack is automatable, though EPSS exploitation probability is very low (0.03%, 9th percentile) and the issue is not listed in CISA KEV.

v1 Apr 30, 2026 - 18:16 CVSS 6.5

GnuTLS performs case-sensitive comparisons of nameConstraints labels in DNS and email certificate constraints, allowing remote attackers to bypass certificate policy validation by crafting leaf certificates with differing character casing in the Subject Alternative Name field. This policy bypass could result in acceptance of certificates that should be rejected, potentially enabling unauthorized access or information disclosure. The vulnerability affects GnuTLS across Red Hat Enterprise Linux 6 through 10 and Red Hat OpenShift Container Platform 4, with no confirmed active exploitation at time of analysis.

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

NVD PRIMARY 7.4 HIGH
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
vuln.today AI 7.4 HIGH

Network-reachable cert validation with no auth (PR:N/UI:N); AC:H because exploitation needs a name-constrained CA deployment; C/I:H from impersonation/policy bypass, no availability impact (A:N).

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
SUSE 6.5 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Red Hat 6.5 MEDIUM

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

Lifecycle Timeline

5
Analysis Updated
Jun 24, 2026 - 17:33 vuln.today
v3 - CVSS changed
Analysis Updated
Jun 24, 2026 - 17:33 vuln.today
v2 - CVSS changed
Severity Changed
Jun 24, 2026 - 17:22 NVD
MEDIUM HIGH
CVSS changed
Jun 24, 2026 - 17:22 NVD
6.5 (MEDIUM) 7.4 (HIGH)
CVE Published
Apr 30, 2026 - 17:37 nvd
MEDIUM 6.5

DescriptionNVD

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.

Executive ViewAI

Why It Matters

GnuTLS certificate validation in Red Hat Enterprise Linux 6-10 and OpenShift Container Platform 4 is vulnerable to a case-sensitivity bypass; publicly available exploit code exists. Attackers can craft certificates that defeat name-constraint validation and impersonate legitimate services, undermining mutual TLS authentication and service-to-service trust. This affects all organizations relying on these Red Hat products for certificate-based access control.

Recommended Action

Within 24 hours: Identify all RHEL 6-10 and OpenShift 4 systems and audit current GnuTLS versions. Within 7 days: Apply vendor-released GnuTLS patch from Red Hat (consult RHSA advisories for CVE-2026-3833 and specific version guidance). Within 30 days: Complete patch rollout across all environments and validate certificate validation behavior on mutual TLS authentication endpoints.

Business Impact: High
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.0%
Top 91% exploitable
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment MSRC Vendor VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.0%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Out-of-Cycle
Exploitation
Poc
System Exposure· derived
Open
Automatable
Yes
Human Impact
High
Technical Impact
Partial

Priority Score

37
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +37
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication Bypass CRITICAL

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Affected Products (CPE)NVD

cpe:2.3:a:red_hat:red_hat_enterprise_linux_10:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_6:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_7:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_8:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_9:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_hardened_images:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_openshift_container_platform_4:*:*:*:*:*:*:*:*

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Same weakness CWE-178 – Improper Handling of Case Sensitivity

View all
CVE-2020-12812 CRITICAL
9.8
CVE-2025-27636 MEDIUM POC
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CVE-2021-24347 HIGH POC
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CVE-2024-5699 CRITICAL POC
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CVE-2023-3545 CRITICAL POC
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CVE-2018-9845 CRITICAL POC
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CVE-2026-53595 CRITICAL POC
9.4
CVE-2026-27588 CRITICAL POC
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Same technique Authentication Bypass

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CVE-2015-3306 CRITICAL POC
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CVE-2023-22515 CRITICAL POC
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CVE-2012-4681 CRITICAL POC
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CVE-2013-2465 CRITICAL POC
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CVE-2011-3544 CRITICAL POC
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CVE-2024-0012 CRITICAL POC
9.3

Vendor StatusVendor

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Micro 5.3 Fixed
SUSE Linux Enterprise Micro 5.4 Fixed
SUSE Linux Enterprise Micro 5.5 Fixed

References

Advisories & patches
ADVISORY https://seclists.org/oss-sec/2026/q4/162 ADVISORY https://ubuntu.com/security/notices/USN-8284-1 ADVISORY https://vuldb.com/vuln/360336 REF https://access.redhat.com/errata/RHSA-2026:13274 REF https://access.redhat.com/errata/RHSA-2026:20611 REF https://access.redhat.com/errata/RHSA-2026:20612 REF https://access.redhat.com/errata/RHSA-2026:20613 REF https://access.redhat.com/errata/RHSA-2026:26319 REF https://access.redhat.com/errata/RHSA-2026:26409 REF https://access.redhat.com/errata/RHSA-2026:29197 REF https://access.redhat.com/errata/RHSA-2026:30004 REF https://access.redhat.com/errata/RHSA-2026:30849 REF https://access.redhat.com/errata/RHSA-2026:30850 REF https://access.redhat.com/errata/RHSA-2026:32962 REF https://access.redhat.com/errata/RHSA-2026:33125 REF https://access.redhat.com/errata/RHSA-2026:41921 REF https://access.redhat.com/errata/RHSA-2026:43575 REF https://access.redhat.com/errata/RHSA-2026:57402 REF https://access.redhat.com/errata/RHSA-2026:58981 REF https://access.redhat.com/errata/RHSA-2026:59831 REF https://access.redhat.com/errata/RHSA-2026:60019 REF https://access.redhat.com/errata/RHSA-2026:62409 REF https://access.redhat.com/errata/RHSA-2026:62549 REF https://access.redhat.com/errata/RHSA-2026:65839 REF https://access.redhat.com/errata/RHSA-2026:65851 REF https://access.redhat.com/errata/RHSA-2026:67857 REF https://access.redhat.com/errata/RHSA-2026:72502 REF https://access.redhat.com/errata/RHSA-2026:74674 REF https://access.redhat.com/errata/RHSA-2026:82304 REF https://access.redhat.com/errata/RHSA-2026:82322 REF https://access.redhat.com/errata/RHSA-2026:82347 REF https://access.redhat.com/errata/RHSA-2026:82354 REF https://access.redhat.com/errata/RHSA-2026:82372 REF https://access.redhat.com/errata/RHSA-2026:82857 REF https://access.redhat.com/errata/RHSA-2026:82888 REF https://access.redhat.com/security/cve/CVE-2026-3833 REF https://bugzilla.redhat.com/show_bug.cgi?id=2445763 REF https://gitlab.com/gnutls/gnutls/-/issues/1803

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