CVE-2026-6785
Published: 26 April 2026
Summary
CVE-2026-6785 is a high-severity Out-of-bounds Read (CWE-125) vulnerability in Mozilla Firefox. Its CVSS base score is 8.1 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 20.1th 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-16 (Memory Protection) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Mandates timely identification, reporting, testing, and correction of flaws, directly requiring patches for the memory safety bugs in Firefox and Thunderbird as recommended by Mozilla.
Implements controls to protect system memory from unauthorized code execution, directly mitigating exploitation of memory corruption issues like out-of-bounds reads/writes and use-after-free.
Requires vulnerability scanning to identify presence of known issues like CVE-2026-6785 in deployed Firefox and Thunderbird versions, enabling proactive remediation.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Memory corruption vulnerabilities enabling remote arbitrary code execution in client applications (browser/email client) without privileges or user interaction directly map to T1203 Exploitation for Client Execution.
NVD Description
Memory safety bugs present in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have…
more
been exploited to run arbitrary code. This vulnerability was fixed in Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Deeper analysisAI
CVE-2026-6785 involves multiple memory safety bugs, including those mapped to CWE-125 (Out-of-bounds Read), CWE-416 (Use After Free), and CWE-787 (Out-of-bounds Write), present in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149, and Thunderbird 149. These bugs exhibited evidence of memory corruption, which Mozilla presumes could be exploited with sufficient effort to achieve arbitrary code execution. The vulnerability carries a CVSS v3.1 base score of 8.1 (AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating high severity due to its potential for significant impact.
Remote attackers require no privileges or user interaction to target systems over the network, though exploitation demands high attack complexity. Successful exploitation could enable arbitrary code execution, compromising confidentiality, integrity, and availability with high impact, as attackers could leverage the memory corruption for control over the affected browser or email client processes.
Mozilla's security advisories (MFSA 2026-30 through 2026-33) and associated Bugzilla entries detail the fixes, recommending immediate updates to Firefox 150, Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird 150, or Thunderbird ESR 140.10 to mitigate the issues. No additional workarounds are specified beyond applying these patches.
Details
- CWE(s)