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Mozilla Firefox CVE-2026-12309

| EUVDEUVD-2026-37100 MEDIUM
Buffer Overflow (CWE-119)
2026-06-16 mozilla GHSA-jxv3-hqj6-9g5c
Buffer Overflow Mozilla
Medium
Disputed · 6.5 Vendor: mozilla
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Severity by source

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

Browser memory bugs require user navigation to attacker content (UI:R); no integrity impact observed; confidentiality and availability impacts remain partial.

3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L
4.0 AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
SUSE
CRITICAL
qualitative
Red Hat
6.1 MEDIUM
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
Low
Integrity
None
Availability
Low

Lifecycle Timeline

3
Analysis Generated
Jul 23, 2026 - 16:42 vuln.today
CVE Published
Jun 16, 2026 - 11:52 cve.org
UNKNOWN (no severity yet)
CVE Published
Jun 16, 2026 - 11:52 cve.org
MEDIUM 6.5

DescriptionCVE.org

Memory safety bug fixed in Firefox 152. This vulnerability was fixed in Firefox 152 and Firefox ESR 140.12.

AnalysisAI

Memory safety violation (CWE-119) in Mozilla Firefox allows remote attackers without authentication or elevated privileges to achieve limited confidentiality breach and availability disruption against unpatched browser instances. Affected versions include all Firefox releases prior to 152 and all Firefox ESR releases prior to 140.12, with patches confirmed released by Mozilla across advisories mfsa2026-57, mfsa2026-58, mfsa2026-60, and mfsa2026-61. No public exploit code has been identified and the vulnerability is absent from the CISA KEV catalog; EPSS probability sits at 0.25% (16th percentile), consistent with SSVC exploitation status of 'none' - suggesting low current threat actor interest despite an automatable attack surface.

Technical ContextAI

Firefox's JavaScript engine and rendering pipeline handle large volumes of untrusted memory operations when processing web content. CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) covers the root cause class, which in browser context typically manifests as buffer overflows, out-of-bounds reads, or use-after-free conditions in heap memory. The affected product is identified by CPE cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*, covering all Firefox versions prior to the fix. The tags indicate Red Hat and SUSE ecosystem packages are also affected, meaning downstream Linux distribution packages of Firefox will require separate patching cycles through those vendors' security channels in addition to the upstream Mozilla fix.

RemediationAI

Upgrade Mozilla Firefox to version 152 or later, or Firefox ESR to version 140.12 or later. These are vendor-released patches confirmed by Mozilla across advisories mfsa2026-57 (https://www.mozilla.org/security/advisories/mfsa2026-57/), mfsa2026-58 (https://www.mozilla.org/security/advisories/mfsa2026-58/), mfsa2026-60 (https://www.mozilla.org/security/advisories/mfsa2026-61/), and mfsa2026-61. Enterprises using Red Hat or SUSE distributions should additionally apply OS-vendor security updates for their packaged Firefox version, as the fix must propagate through those distribution channels separately. If immediate patching is not feasible, consider restricting or disabling JavaScript execution for untrusted sites via browser policy, though this carries significant usability trade-offs. Network-level filtering of untrusted web content at the proxy layer is a lower-impact workaround but does not eliminate risk from trusted-appearing but compromised sites.

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Same weakness CWE-119 – Buffer Overflow

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CVE-2020-0796 CRITICAL POC
10.0
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7.8
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CVE-2013-3918 HIGH POC
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-2017-7269 CRITICAL POC
9.8
CVE-2015-5119 CRITICAL POC
9.8
CVE-2015-3113 CRITICAL POC
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CVE-2020-0796 CRITICAL POC
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CVE-2019-11043 CRITICAL POC
9.8
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-2026-12309 vulnerability details – vuln.today
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