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Firefox NSS CVE-2026-6766

| EUVDEUVD-2026-24107 HIGH
Improper Check for Unusual or Exceptional Conditions (CWE-754)
2026-04-21 mozilla GHSA-q6qg-6fmg-jjcv
Information Disclosure Mozilla Red Hat Suse
7.5
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
SUSE
HIGH
qualitative
Red Hat
6.1 MEDIUM
qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Lifecycle Timeline

8
Patch released
Apr 29, 2026 - 02:30 nvd
Patch available
Analysis Updated
Apr 22, 2026 - 00:36 vuln.today
v2 (cvss_changed)
Re-analysis Queued
Apr 22, 2026 - 00:22 vuln.today
cvss_changed
Analysis Generated
Apr 21, 2026 - 17:23 vuln.today
CVSS changed
Apr 21, 2026 - 17:22 NVD
7.5 (HIGH)
EUVD ID Assigned
Apr 21, 2026 - 13:15 euvd
EUVD-2026-24107
Analysis Generated
Apr 21, 2026 - 13:15 vuln.today
CVE Published
Apr 21, 2026 - 12:40 nvd
HIGH 7.5

DescriptionCVE.org

Incorrect boundary conditions in the Libraries component in NSS. This vulnerability was fixed in Firefox 150 and Firefox ESR 140.10.

AnalysisAI

Remote information disclosure in Mozilla Network Security Services (NSS) library allows unauthenticated attackers to extract high-sensitivity data via network requests with no user interaction. Affects Firefox versions prior to 150 and Firefox ESR prior to 140.10. The vulnerability stems from incorrect boundary condition handling (CWE-754) in NSS cryptographic libraries. Vendor-released patches available in Firefox 150 and Firefox ESR 140.10. SSVC framework classifies as automatable with partial technical impact, though no public exploit identified at time of analysis.

Technical ContextAI

Network Security Services (NSS) is Mozilla's cryptographic library providing SSL/TLS protocol implementation and certificate validation used across Firefox, Thunderbird, and other Mozilla products. This vulnerability involves incorrect boundary condition checks (CWE-754) in library components, where improper validation of input size or buffer boundaries can lead to reading memory outside intended bounds. Boundary condition errors in cryptographic libraries are particularly sensitive as they may expose key material, session tokens, or other confidential data processed during TLS handshakes or certificate operations. The CPE identifier confirms impact to the Firefox application component that integrates NSS, with the library's use extending beyond just web browsing to email clients and other network-aware Mozilla applications.

RemediationAI

Upgrade to Firefox version 150 or later for standard release channel, or Firefox ESR version 140.10 or later for extended support deployments. Mozilla security advisories confirm patches in MFSA2026-30 (https://www.mozilla.org/security/advisories/mfsa2026-30/) and MFSA2026-32 (https://www.mozilla.org/security/advisories/mfsa2026-32/) for Firefox 150, with ESR fixes detailed in MFSA2026-33 and MFSA2026-34. Organizations unable to immediately patch should implement network-level monitoring for anomalous TLS handshake patterns or unexpected data exfiltration from Firefox processes, though this provides only detection not prevention. For high-security environments, restrict Firefox usage to non-sensitive contexts until patching is complete, or temporarily substitute alternative browsers for confidential transactions, accepting potential workflow disruption. No effective compensating controls exist for boundary condition vulnerabilities in cryptographic libraries short of disabling affected functionality entirely.

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Vendor StatusVendor

SUSE

Severity: High
Product Status
SUSE Liberty Linux 10 Fixed
SUSE Liberty Linux 8 Fixed
SUSE Liberty Linux 9 Fixed
SUSE Linux Enterprise Server 16.0 SUSE Linux Enterprise Server for SAP applications 16.0 Fixed
openSUSE Leap 16.0 Fixed

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CVE-2026-6766 vulnerability details – vuln.today
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