CVE-2026-5732
Published: 07 April 2026
Summary
CVE-2026-5732 is a high-severity Integer Overflow or Wraparound (CWE-190) vulnerability in Mozilla Firefox. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 17.8th 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).
Deeper analysis
CVE-2026-5732 is an integer overflow vulnerability caused by incorrect boundary conditions in the Graphics: Text component. It affects Mozilla Firefox prior to version 149.0.2, Firefox ESR prior to 140.9.1, Thunderbird prior to 149.0.2, and Thunderbird prior to 140.9.1. The issue is classified under CWE-190 (Integer Overflow or Wraparound).
The vulnerability carries a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H), denoting high severity. Remote attackers with no privileges can exploit it over the network with low attack complexity, though it requires user interaction. Successful exploitation enables high-impact violations of confidentiality, integrity, and availability.
Mozilla advisories detail the fix in Firefox 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1. Mitigation involves updating to these patched versions. Additional technical details are provided in Mozilla Security Advisories MFSA2026-25, MFSA2026-27, MFSA2026-28, MFSA2026-29, and Bugzilla bug 2017867.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-19611
Vulnerability details
Incorrect boundary conditions, integer overflow in the Graphics: Text component. This vulnerability was fixed in Firefox 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Integer overflow in Mozilla Firefox/Thunderbird graphics component enables remote exploitation of client application for code execution with user interaction required, directly mapping to T1203 Exploitation for Client Execution.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
SI-2 requires timely identification and remediation of flaws like the integer overflow in Firefox's Graphics: Text component by applying vendor patches such as Firefox 149.0.2.
SI-16 implements memory protections like ASLR and DEP that mitigate exploitation of the integer overflow vulnerability even if unpatched.
RA-5 uses vulnerability scanning to detect systems running vulnerable versions of Firefox or Thunderbird affected by CVE-2026-5732.