Executive brief
A vulnerability exists in the text and font processing component of Mozilla Firefox and Thunderbird. This flaw could allow a remote attacker to cause a service outage or application crash by providing specially crafted content. This impact primarily affects the availability of the browser or email client during operation.
Technical details
The vulnerability is caused by incorrect boundary conditions (CWE-754) within the 'Layout: Text and Fonts' component of Mozilla browsers and mail clients. Red Hat's analysis further classifies this as an out-of-bounds write (CWE-787). An attacker can exploit this over the network without authentication or user interaction to trigger a denial-of-service (DoS) condition, typically manifested as an application crash. The issue is resolved in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Affected products
- Mozilla Firefox < 149
- Mozilla Firefox ESR < 115.34, < 140.9
- Mozilla Thunderbird < 149, < 140.9
- Red Hat Lightspeed Red Hat Enterprise Linux Server 7 ELS
Timeline
- 2026-03-24: disclosed
- 2026-03-24: patched
- 2026-03-24: advisory
References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2021863
- https://www.mozilla.org/security/advisories/mfsa2026-20/
- https://www.mozilla.org/security/advisories/mfsa2026-21/
- https://www.mozilla.org/security/advisories/mfsa2026-22/
- https://www.mozilla.org/security/advisories/mfsa2026-23/
- https://www.mozilla.org/security/advisories/mfsa2026-24/
- https://access.redhat.com/errata/RHSA-2026:5930