Denial-of-Service Vulnerability in Firefox by Mozilla
CVE-2026-4726

7.5HIGH

Key Information:

Vendor

Mozilla
Status
Firefox
Thunderbird
Vendor
CVE Published:
24 March 2026

What is CVE-2026-4726?

A denial-of-service vulnerability exists in the XML component of Firefox, impacting all versions prior to 149. This flaw can be exploited to disrupt the normal functioning of the browser, leading to potential service outages and a negative user experience. Ensuring that your Firefox installation is updated is critical to maintaining a secure browsing environment.

Affected Version(s)

Firefox < 149

Thunderbird < 149

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1955311
https://www.mozilla.org/security/advisories/mfsa2026-20/
https://www.mozilla.org/security/advisories/mfsa2026-23/

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Hanno Boeck
.