CVE-2026-4690
Published: 24 March 2026
Summary
CVE-2026-4690 is a high-severity Integer Overflow or Wraparound (CWE-190) vulnerability in Mozilla Firefox. Its CVSS base score is 8.6 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 4.6th 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 SC-39 (Process Isolation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly mandates timely identification, reporting, and correction of flaws such as the integer overflow and boundary condition error in the XPCOM sandbox component via patching to fixed Firefox and Thunderbird versions.
Implements memory protection mechanisms that defend against exploitation of integer overflows leading to buffer overflows and sandbox escapes.
Enforces process isolation to strengthen sandbox boundaries and mitigate escapes resulting from flaws in components like XPCOM.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Sandbox escape via remote client exploitation enables privilege escalation (T1068) and client-side code execution (T1203); high availability impact directly supports DoS via application exploitation (T1499.004).
NVD Description
Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM 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-2026-4690 is a sandbox escape vulnerability stemming from incorrect boundary conditions and an integer overflow in the XPCOM component. It affects Mozilla Firefox versions prior to 149, Firefox ESR prior to 115.34 and 140.9, Thunderbird prior to 149 and 140.9. The issue is rated with a CVSS v3.1 base score of 8.6 and is associated with CWEs 190 (Integer Overflow or Wraparound), 754 (Improper Check for Unusual or Exceptional Conditions), and 120 (Buffer Copy without Checking Size of Input).
A remote attacker requires no privileges or user interaction and can exploit this over the network with low complexity. Successful exploitation results in a sandbox escape with a changed scope, leading to high availability impact such as denial of service, though without direct confidentiality or integrity violations.
Mozilla's security advisories (MFSA 2026-20 through 2026-23) and the associated Bugzilla entry detail the patch, recommending immediate updates to Firefox 149, Firefox ESR 115.34 or 140.9, Thunderbird 149, or Thunderbird 140.9 to mitigate the vulnerability.
Details
- CWE(s)