Memory Safety Bugs in Mozilla's Firefox and Thunderbird Products
CVE-2026-6786

8.1HIGH

Key Information:

Vendor

Mozilla
Status
Firefox
Vendor
CVE Published:
21 April 2026

What is CVE-2026-6786?

Mozilla's Firefox and Thunderbird products have been found to contain memory safety vulnerabilities, specifically in versions ESR 140.9 and 149. These vulnerabilities exhibit signs of memory corruption, raising concerns regarding potential exploitation to execute arbitrary code. The issues were addressed in Firefox version 150 and Firefox ESR 140.10, emphasizing the importance of timely updates to safeguard user data and application integrity.

Affected Version(s)

Firefox 140.10

Firefox 150

References

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2010727%2...
https://www.mozilla.org/security/advisories/mfsa2026-30/
https://www.mozilla.org/security/advisories/mfsa2026-32/

CVSS V3.1

Score:
8.1
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
High
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Alex Franchuk, Andrew McCreight, Brian Grinstead, Christian Holler, Jan de Mooij, Maurice Dauer, Sebastian Hengst, Tom Schuster and the Mozilla Fuzzing Team
.