Cyber Posture

CVE-2026-2764

Critical

Published: 24 February 2026

Published
24 February 2026
Modified
13 April 2026
KEV Added
—
Patch
—
CVSS Score 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0003 7.2th percentile
Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Description

JIT miscompilation, use-after-free in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match
prevent

Directly requires timely identification, prioritization, and patching of the JIT miscompilation use-after-free flaw in vulnerable Firefox and Thunderbird versions to eliminate remote code execution risk.

SI-5 Security Alerts, Advisories, and Directives partial match
prevent

Ensures reception and implementation of vendor security advisories like MFSA 2026-13 announcing CVE-2026-2764, prompting updates to fixed versions.

RA-5 Vulnerability Monitoring and Scanning partial match
detect

Deploys vulnerability scanning to identify systems running affected Firefox or Thunderbird versions prior to exploitation via malicious web content.

Security SummaryAI

CVE-2026-2764 is a high-severity vulnerability involving JIT miscompilation that leads to a use-after-free condition in the JavaScript Engine's JIT component. It affects Mozilla Firefox and Thunderbird prior to the following fixed versions: Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8. Classified under CWE-416 with a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), the flaw enables severe impacts without requiring user privileges or interaction.

Remote attackers can exploit this vulnerability over the network with low complexity by delivering malicious web content that triggers the JIT miscompilation and use-after-free error. No authentication or user interaction is needed, allowing unauthenticated adversaries to achieve high confidentiality, integrity, and availability impacts, potentially resulting in arbitrary code execution within the browser's sandboxed environment.

Mozilla's security advisories (MFSA 2026-13 through 2026-16) and the associated Bugzilla entry (bug 2012608) confirm the issue was addressed in the listed patches. Security practitioners should prioritize updating affected Firefox and Thunderbird installations to the fixed versions to mitigate exploitation risks.

Details

CWE(s)
CWE-416

Affected Products

mozilla
firefox
≤ 115.33.0 · ≤ 148.0 · 128.0 — 140.8.0
mozilla
thunderbird
≤ 140.8.0 · ≤ 148.0

MITRE ATT&CK Enterprise TechniquesAI

T1189 Drive-by Compromise Initial Access
Adversaries may gain access to a system through a user visiting a website over the normal course of browsing.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
Why these techniques?

CVE enables remote arbitrary code execution via malicious web/JS content with no auth/UI required, directly mapping to drive-by compromise via crafted sites and exploitation for client execution in browser/email clients.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

References