Cyber Posture

CVE-2026-4697

High

Published: 24 March 2026

Published
24 March 2026
Modified
13 April 2026
KEV Added
—
Patch
—
CVSS Score 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.0002 6.0th percentile
Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Description

Incorrect boundary conditions in the Audio/Video: Web Codecs component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Mitigating Controls (NIST 800-53 r5)AI

SI-2 Flaw Remediation good match
prevent

Directly requires timely identification, testing, and application of patches to remediate the specific boundary condition flaw in the Web Codecs component of Firefox and Thunderbird.

RA-5 Vulnerability Monitoring and Scanning partial match
detect

Mandates vulnerability scanning to identify systems running vulnerable versions of Mozilla products affected by CVE-2026-4697.

SC-5 Denial-of-service Protection partial match
prevent

Implements controls to limit or detect the effects of denial-of-service attacks exploiting this vulnerability to cause application crashes.

Security SummaryAI

CVE-2026-4697 involves incorrect boundary conditions (CWE-754) in the Audio/Video: Web Codecs component of Mozilla products. This vulnerability affects Firefox, Firefox ESR, and Thunderbird, with fixes released in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

The vulnerability carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Remote attackers with no privileges or user interaction can exploit it over the network with low attack complexity, achieving a high impact on availability through denial of service, such as application crashes, without compromising confidentiality or integrity.

Mozilla's security advisories MFSA 2026-20, MFSA 2026-22, MFSA 2026-23, and MFSA 2026-24, along with Bugzilla entry 2020422, provide further details on the issue and patches. Security practitioners should ensure affected systems update to the specified fixed versions for mitigation.

Details

CWE(s)
CWE-754

Affected Products

mozilla
firefox
≤ 140.9.0 · ≤ 149.0

MITRE ATT&CK Enterprise TechniquesAI

T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
Why these techniques?

The vulnerability allows remote network exploitation of a client-side boundary condition flaw in web codecs, directly causing application crashes and high availability impact with no privileges or user interaction required, mapping precisely to application/system exploitation for endpoint DoS.

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

References