CVE-2026-6753
Published: 21 April 2026
Summary
CVE-2026-6753 is a high-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability in Mozilla Firefox. Its CVSS base score is 7.3 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 22.4th 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 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-6753 involves incorrect boundary conditions in the WebRTC component, classified under CWE-119. This vulnerability affects Mozilla Firefox versions prior to 150, Firefox ESR prior to 140.10, Thunderbird prior to 150, and Thunderbird prior to 140.10. It was published on 2026-04-21 and carries a CVSS v3.1 base score of 7.3 (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L), indicating high severity due to its network accessibility and low barriers to exploitation.
Remote attackers can exploit this vulnerability over the network with low attack complexity, requiring no privileges, user interaction, or special conditions. Successful exploitation allows limited impacts, including partial disclosure of sensitive information, partial modification of data, and partial denial of service.
Mozilla security advisories (MFSA 2026-30, 32, 33, and 34) and the associated Bugzilla entry (bug 2027501) detail the fix applied in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10, recommending immediate upgrades to these versions for mitigation.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-24094
Vulnerability details
Incorrect boundary conditions in the WebRTC component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Memory corruption (CWE-119) in client-side WebRTC component of Firefox/Thunderbird enables remote exploitation for client execution (T1203) with no privileges or user interaction required.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires organizations to identify, report, and correct system flaws like the WebRTC boundary condition error (CWE-119), directly enabling timely patching as provided in Firefox 150 and ESR 140.10.
Mandates vulnerability scanning to identify deployed vulnerable versions of Firefox and Thunderbird affected by this remotely exploitable WebRTC flaw.
Ensures monitoring and dissemination of vendor security advisories like MFSA 2026-30, facilitating awareness and application of fixes for this CVE.