CVE-2026-4707
Published: 24 March 2026
Summary
CVE-2026-4707 is a high-severity Improper Check for Unusual or Exceptional Conditions (CWE-754) vulnerability in Mozilla Firefox. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 5.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and RA-5 (Vulnerability Monitoring and Scanning).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly requires timely remediation of flaws like CVE-2026-4707 through patching Firefox and Thunderbird to fixed versions, preventing remote DoS exploitation.
Provides vulnerability scanning to identify systems with vulnerable Firefox or Thunderbird versions affected by CVE-2026-4707's boundary condition flaw.
Ensures monitoring of security advisories such as Mozilla MFSA 2026-20 to promptly learn of and apply fixes for CVE-2026-4707.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
CVE describes remote unauthenticated exploitation of a boundary condition flaw in Firefox/Thunderbird Canvas2D that directly produces application crashes (high availability impact, no other effects), matching T1499.004 Application or System Exploitation for Endpoint Denial of Service.
NVD Description
Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Deeper analysisAI
CVE-2026-4707 is a vulnerability involving incorrect boundary conditions in the Graphics: Canvas2D component of Mozilla Firefox and Thunderbird. It affects versions of Firefox prior to 149, Firefox ESR prior to 115.34 and 140.9, and Thunderbird prior to 149 and 140.9. The issue is classified under CWE-754 (Improper Check for Unusual or Exceptional Conditions) and carries a CVSS v3.1 base score of 7.5.
An unauthenticated attacker can exploit this vulnerability remotely over the network with low complexity and no user interaction required. Successful exploitation leads to a denial-of-service condition with high availability impact, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), potentially causing browser or application crashes.
Mozilla security advisories (MFSA 2026-20 through 2026-23) and the associated Bugzilla entry detail the fix applied in the listed versions. Security practitioners should prioritize updating affected Firefox and Thunderbird installations to mitigate the risk.
Details
- CWE(s)