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Firefox ESR CVE-2026-12329

| EUVDEUVD-2026-37075 MEDIUM
Buffer Overflow (CWE-119)
2026-06-16 mozilla GHSA-2g6w-7hp8-fv93
Buffer Overflow Mozilla
Medium
Disputed · 5.3 Vendor: mozilla
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Severity by source

Sources disagree (Medium–Critical)
Vendor (mozilla) PRIMARY
5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
vuln.today AI
4.3 MEDIUM

Browser memory bug requires passive user navigation to malicious content (UI:R); no confidentiality or integrity impact applies, only partial availability.

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
4.0 AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
SUSE
CRITICAL
qualitative
Red Hat
7.5 HIGH
qualitative

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: mozilla

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

Lifecycle Timeline

3
Analysis Generated
Jul 23, 2026 - 16:39 vuln.today
CVE Published
Jun 16, 2026 - 11:53 cve.org
UNKNOWN (no severity yet)
CVE Published
Jun 16, 2026 - 11:53 cve.org
MEDIUM 5.3

DescriptionCVE.org

Memory safety bug fixed in Firefox ESR 140.12. This vulnerability was fixed in Firefox ESR 140.12.

AnalysisAI

Memory safety vulnerability (CWE-119 buffer overflow class) in Mozilla Firefox ESR prior to version 140.12 enables remote unauthenticated attackers to cause a partial denial of service by triggering a browser crash. The CVSS vector confirms network delivery with no privileges or user interaction required per vendor scoring, and impact is limited strictly to availability (A:L) with no confidentiality or integrity consequences. No public exploit code has been identified at time of analysis, and EPSS at 0.25% (16th percentile) places this well below typical exploitation thresholds despite its automatable delivery vector.

Technical ContextAI

CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) covers the broad class of buffer overflows and out-of-bounds memory access bugs rooted in incorrect bounds checking during memory operations. Mozilla Firefox ESR (Extended Support Release) is the long-term-support branch of the Firefox browser, targeted at organizations requiring extended patch stability. The affected CPE cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* covers all Firefox versions prior to the fix, though the description explicitly scopes the fix to the ESR 140.12 release line. The vulnerability resides in the browser engine's memory management subsystem; the exact component is referenced in Mozilla's Bugzilla tracker (bug 2044738). Multiple Red Hat Enterprise Linux distributions package Firefox ESR and have issued their own errata (RHSA-2026:27717, RHSA-2026:27733, RHSA-2026:27734, RHSA-2026:29940, RHSA-2026:30846, RHSA-2026:33445, RHSA-2026:36100), confirming downstream impact.

RemediationAI

The primary fix is upgrading to Firefox ESR 140.12, confirmed by Mozilla's official advisories at https://www.mozilla.org/security/advisories/mfsa2026-58/ and https://www.mozilla.org/security/advisories/mfsa2026-61/. Red Hat Enterprise Linux users should apply the appropriate RHSA errata listed above via standard package management (yum/dnf update firefox). As a compensating control where immediate patching is not feasible, restricting access to untrusted or arbitrary web content through DNS filtering, web proxy category blocking, or browser extension-based content controls can reduce exposure. Browser crash recovery is automatic in Firefox (tab restore), so availability impact is self-limiting in most user workflows. No significant trade-offs are associated with the primary patch upgrade.

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Same weakness CWE-119 – Buffer Overflow

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7.8
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8.8
CVE-2023-4966 HIGH POC
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CVE-2017-11774 HIGH POC
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Same technique Buffer Overflow

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CVE-2020-0796 CRITICAL POC
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CVE-2019-11043 CRITICAL POC
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CVE-2009-0927 HIGH POC
8.8
CVE-2012-1889 HIGH POC
8.8

Vendor StatusVendor

SUSE

Severity: Critical
Product Status
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS Affected

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CVE-2026-12329 vulnerability details – vuln.today
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