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Firefox Esr EUVDEUVD-2026-14857

| CVE-2026-4721 CRITICAL
Classic Buffer Overflow (CWE-120)
2026-03-24 mozilla
9.8
CVSS 3.1 · Vendor: mozilla
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Severity by source

Vendor (mozilla) 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 Vendor (mozilla).

CVSS VectorVendor: mozilla

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-2026-14857
Analysis Generated
Mar 24, 2026 - 12:45 vuln.today
CVE Published
Mar 24, 2026 - 12:30 nvd
CRITICAL 9.8

DescriptionCVE.org

Memory safety bugs present in Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9.

AnalysisAI

Multiple memory safety bugs affecting Firefox, Firefox ESR, and Thunderbird browsers present a critical remote code execution risk through memory corruption vulnerabilities. The affected versions include Firefox below 149, Firefox ESR below 115.34 and 140.9, Thunderbird ESR 140.8, Firefox 148, and Thunderbird 148. These memory safety issues demonstrate evidence of exploitable memory corruption that could allow attackers to execute arbitrary code on affected systems, though no public exploit or active KEV confirmation is currently documented.

Technical ContextAI

The vulnerability class involves memory safety bugs across the Mozilla Firefox and Thunderbird application codebases, as identified through the CPE entries cpe:2.3:a:mozilla:firefox, cpe:2.3:a:mozilla:firefox_esr, and cpe:2.3:a:mozilla:thunderbird_esr. While specific CWE identifiers are not provided in this advisory, the tags indicate buffer overflow and memory corruption vulnerabilities are present. The underlying issue relates to unsafe memory handling in the browser's core rendering engine and related subsystems, where multiple discrete bugs (referenced by 16 distinct Mozilla bug IDs spanning 2013762 through 2022676) collectively demonstrate memory corruption with arbitrary code execution potential. These bugs were identified through fuzzing, code review, and security analysis of the browser's C++ codebase.

RemediationAI

Immediately upgrade Mozilla Firefox to version 149 or later, Firefox ESR to version 115.34 or later (for the 115.x branch) or 140.9 or later (for the 140.x branch), and Thunderbird to the corresponding patched versions. Users should enable automatic updates in browser settings to receive patches immediately upon release. Organizations managing Firefox deployments should prioritize patching through their software distribution mechanisms within 24-48 hours. No effective workarounds exist for memory corruption vulnerabilities in browser engines; patching is the only reliable mitigation. Users unable to patch immediately should restrict browsing to trusted sites and consider using additional security controls such as browser sandboxing, endpoint detection and response (EDR) solutions, and network-level filtering. Consult Mozilla security 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 version-specific remediation details.

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7.5 Sep 25

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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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EUVD-2026-14857 vulnerability details – vuln.today

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