CVE-2026-6763
Published: 21 April 2026
Description
Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Implements a reliable, tamperproof protection mechanism whose completeness can be assured.
Procedures for training on protection mechanisms reduce the chance of protection mechanism failures being present or exploitable.
Documented procedures to implement assessment, authorization, and monitoring controls prevent these protection mechanisms from failing due to undefined processes.
Direct evaluation of whether controls produce desired security outcomes detects protection mechanism failures and enables remediation.
Requires assessment that protection mechanisms are correctly implemented and producing intended security outcomes.
The POA&M process ensures identified weaknesses in protection mechanisms are documented and scheduled for remediation, reducing the duration they remain exploitable.
Ongoing control assessments and analysis of monitoring data enable timely detection and response when protection mechanisms fail.
Impact analysis identifies changes that could weaken or disable existing protection mechanisms.
Security SummaryAI
CVE-2026-6763 is a mitigation bypass vulnerability in the File Handling component of Mozilla products, specifically affecting Firefox versions prior to 150, Firefox ESR versions prior to 140.10, Thunderbird versions prior to 150, and Thunderbird versions prior to 140.10. Published on 2026-04-21, it carries a CVSS v3.1 base score of 6.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N) and is associated with CWE-693 (Protection Mechanism Failure).
Remote attackers require no privileges or user interaction to exploit this vulnerability over the network with low complexity. Successful exploitation enables limited impacts on confidentiality and integrity, allowing attackers to bypass mitigations in the File Handling component.
Mozilla security advisories (MFSA2026-30 through MFSA2026-34) and the associated Bugzilla entry detail the patch, recommending immediate upgrades to Firefox 150, Firefox ESR 140.10, Thunderbird 150, or Thunderbird 140.10 to mitigate the issue.
Details
- CWE(s)
Affected Products
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Bypass of file handling mitigations in browser/email client enables remote exploitation for drive-by compromise and client execution without user interaction.