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Firefox Esr CVE-2026-4696

| EUVDEUVD-2026-14811 CRITICAL
Use After Free (CWE-416)
2026-03-24 mozilla GHSA-h22r-8qx2-2mv3
9.8
CVSS 3.1 · NVD
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Severity by source

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

Primary rating from NVD.

CVSS VectorNVD

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

Lifecycle Timeline

4
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
EUVD ID Assigned
Mar 24, 2026 - 12:45 euvd
EUVD-2026-14811
Analysis Generated
Mar 24, 2026 - 12:45 vuln.today
CVE Published
Mar 24, 2026 - 12:30 nvd
CRITICAL 9.8

DescriptionNVD

Use-after-free in the Layout: Text and Fonts component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9.

AnalysisAI

Unauthenticated remote attackers can achieve arbitrary code execution through a use-after-free memory corruption vulnerability in Firefox's text and font rendering engine, affecting Firefox versions below 149, ESR below 115.34, and ESR below 140.9. The vulnerability requires no user interaction or special privileges and allows complete compromise of confidentiality, integrity, and availability. No patch is currently available.

Technical ContextAI

The vulnerability resides in Firefox's text and font rendering subsystem, which is responsible for parsing, measuring, and displaying font data and text layout operations. Use-after-free vulnerabilities occur when memory is accessed after it has been deallocated, typically when an object's lifecycle management fails or when reference counting is incorrect. In the context of text rendering, this could manifest when font objects, glyph caches, or text layout structures are freed prematurely while still referenced by active rendering operations. The affected products identified via CPE are Mozilla Firefox (all versions) and Mozilla Firefox ESR (all versions), with the ESR branches maintaining separate version tracks for extended support customers. The root cause falls under CWE categories related to improper memory management and use-after-free conditions common in C/C++ rendering engines.

RemediationAI

Immediately upgrade Mozilla Firefox to version 149 or later, and upgrade Firefox ESR installations to version 115.34 or later (for the ESR 115 branch) or version 140.9 or later (for the ESR 140 branch). Automated update mechanisms in Firefox will deploy patched versions; manual updates are available through the Help menu (Firefox menu > Help > About Firefox) or from https://www.mozilla.org/firefox/. For enterprise environments using Firefox ESR, deploy updates via your standard patch management processes and verify update completion across all endpoints. Users who cannot immediately patch should consider temporarily restricting Firefox usage to trusted websites only and disabling JavaScript for untrusted content as a temporary mitigation, though patching remains the only reliable fix. Review the detailed advisories at https://www.mozilla.org/security/advisories/mfsa2026-20/, https://www.mozilla.org/security/advisories/mfsa2026-21/, and https://www.mozilla.org/security/advisories/mfsa2026-22/ for any additional guidance.

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Vendor StatusVendor

Debian

firefox
Release Status Fixed Version Urgency
sid vulnerable 148.0.2-1 -
(unstable) fixed (unfixed) -
firefox-esr
Release Status Fixed Version Urgency
bullseye vulnerable 115.14.0esr-1~deb11u1 -
bullseye (security) vulnerable 140.8.0esr-1~deb11u1 -
bookworm vulnerable 128.14.0esr-1~deb12u1 -
bookworm (security) vulnerable 140.8.0esr-1~deb12u1 -
trixie (security), trixie vulnerable 140.8.0esr-1~deb13u1 -
forky, sid vulnerable 140.8.0esr-1 -
(unstable) fixed (unfixed) -

SUSE

Severity: Critical
Product Status
Image SLES15-SP5-SAP-Azure-LI-BYOS Image SLES15-SP5-SAP-Azure-LI-BYOS-Production Image SLES15-SP5-SAP-Azure-VLI-BYOS Image SLES15-SP5-SAP-Azure-VLI-BYOS-Production Image SLES15-SP6-SAP-Azure-LI-BYOS Image SLES15-SP6-SAP-Azure-LI-BYOS-Production Image SLES15-SP6-SAP-Azure-VLI-BYOS Image SLES15-SP6-SAP-Azure-VLI-BYOS-Production Image SLES15-SP7-SAP-Azure-LI-BYOS-Production Image SLES15-SP7-SAP-Azure-VLI-BYOS-Production Affected
SUSE Liberty Linux 10 Fixed
SUSE Liberty Linux 8 Fixed
SUSE Liberty Linux 9 Fixed
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed

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CVE-2026-4696 vulnerability details – vuln.today

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