Memory Safety Bugs in Firefox and Thunderbird by Mozilla
CVE-2026-4729

9.8CRITICAL

Key Information:

Vendor

Mozilla
Status
Firefox
Thunderbird
Vendor
CVE Published:
24 March 2026

What is CVE-2026-4729?

Mozilla has identified memory safety issues in versions of Firefox and Thunderbird prior to 149, which could lead to potential memory corruption. These vulnerabilities exhibit characteristics that may allow attackers to exploit them to execute arbitrary code. It is recommended that users update to the latest versions to mitigate these risks and ensure the integrity of their systems.

Affected Version(s)

Firefox < 149

Thunderbird < 149

References

https://bugzilla.mozilla.org/buglist.cgi?bug_id=1944033%2...
https://www.mozilla.org/security/advisories/mfsa2026-20/
https://www.mozilla.org/security/advisories/mfsa2026-23/

CVSS V3.1

Score:
9.8
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Christian Holler, Fatih Kilic, Tom Schuster and the Mozilla Fuzzing Team
.