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Mozilla Firefox CVE-2026-12291

| EUVDEUVD-2026-37082 HIGH
Use After Free (CWE-416)
2026-06-16 mozilla GHSA-cvpf-j74m-qjrj
Mozilla Use After Free Memory Corruption Information Disclosure
8.8
CVSS 3.1 · Vendor: mozilla
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Severity by source

Vendor (mozilla) PRIMARY
8.8 HIGH
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
vuln.today AI
7.5 HIGH

Network-reachable via web content with no auth (AV:N/PR:N); requires user to visit page (UI:R) and winning a memory race for UAF justifies AC:H; full memory corruption yields C/I/A:H.

3.1 AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
4.0 AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
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:R/S:U/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

3
Analysis Generated
Jun 18, 2026 - 19:38 vuln.today
CVSS changed
Jun 18, 2026 - 19:38 NVD
8.8 (None) 8.8 (HIGH)
CVE Published
Jun 16, 2026 - 11:52 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

Use-after-free in the Networking: HTTP component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, and Firefox ESR 115.37.

AnalysisAI

Memory corruption via use-after-free in the Networking: HTTP component of Mozilla Firefox enables remote attackers to potentially execute arbitrary code or trigger crashes when a user visits a malicious page. The flaw affects Firefox prior to version 152, Firefox ESR before 140.12, and Firefox ESR before 115.37, and carries a CVSS 3.1 score of 8.8 with high impact across confidentiality, integrity, and availability. With an EPSS of 0.16% (5th percentile) and no public exploit identified at time of analysis, opportunistic mass exploitation appears unlikely despite the high severity rating.

Technical ContextAI

The vulnerability is classified as CWE-416 (Use After Free), a memory-safety class where freed memory is dereferenced or reused, often allowing attacker-controlled data to occupy the previously freed allocation and influence subsequent operations. The defect lives in Firefox's Networking: HTTP component, which parses and manages HTTP request/response lifecycles, connection pooling, and resource handling in the Gecko engine. In browser HTTP stacks, use-after-free conditions typically arise from races between connection teardown, redirect handling, or stream cancellation and concurrent callbacks holding stale pointers to channel or transaction objects. Per CPE data (cpe:2.3:a:mozilla:firefox), Firefox desktop builds are affected, and Mozilla advisories MFSA2026-57 through MFSA2026-61 indicate parallel publication across Firefox and the ESR 140.x and 115.x branches.

RemediationAI

Vendor-released patch: Firefox 152, Firefox ESR 140.12, and Firefox ESR 115.37 - upgrade to one of these versions per the Mozilla advisories at https://www.mozilla.org/security/advisories/mfsa2026-57/, mfsa2026-58, mfsa2026-59, mfsa2026-60, and mfsa2026-61. Enterprises pinned to ESR should align with the matching ESR train (140.12 for current ESR, 115.37 for the legacy ESR being phased out) and push updates via existing management tooling such as Group Policy, Intune, or Jamf. As a temporary compensating control where patching is delayed, restrict browsing to trusted sites via web proxy or DNS filtering and consider enforcing strict site isolation; disabling HTTP/2 or HTTP/3 in about:config is not recommended as a workaround since it degrades performance and is unlikely to fully neutralize a UAF in the broader networking stack. No standalone workaround is published by Mozilla, so patching is the authoritative remediation.

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Same weakness CWE-416 – Use After Free

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CVE-2019-0708 CRITICAL POC
9.8
CVE-2015-5119 CRITICAL POC
9.8
CVE-2014-0322 HIGH POC
8.8
CVE-2012-4792 HIGH POC
8.8
CVE-2009-4324 HIGH POC
7.8
CVE-2015-0313 CRITICAL POC
9.8
CVE-2015-5122 CRITICAL POC
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CVE-2013-2551 HIGH POC
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Same technique Use After Free

View all
CVE-2015-5119 CRITICAL POC
9.8
CVE-2014-0322 HIGH POC
8.8
CVE-2012-4792 HIGH POC
8.8
CVE-2009-4324 HIGH POC
7.8
CVE-2015-0313 CRITICAL POC
9.8
CVE-2015-5122 CRITICAL POC
9.8
CVE-2013-2551 HIGH POC
8.8
CVE-2012-4969 HIGH POC
8.1

Vendor StatusVendor

SUSE

Severity: Critical
Product Status
SUSE Liberty Linux 8 Fixed
SUSE Liberty Linux 9 Fixed
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise High Performance Computing 15 SP7 SUSE Linux Enterprise Module for Desktop Applications 15 SP7 SUSE Linux Enterprise Server 15 SP7 SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Fixed

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CVE-2026-12291 vulnerability details – vuln.today
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