CVE-2013-1720: Mozilla Firefox

Medium severity, CVSS 6.8. EPSS: 4% chance of exploitation in the next 30 days.

The nsHtml5TreeBuilder::resetTheInsertionMode function in the HTML5 Tree Builder in Mozilla Firefox before 24.0, Thunderbird before 24.0, and SeaMonkey before 2.21 does not properly maintain the state of the insertion-mode stack for template elements, which allows remote attackers to execute arbitrary code or cause a denial of service (heap-based buffer over-read) by triggering use of this stack in its empty state.

Affected products

• Mozilla Firefox: up to and including 23.0.1; version 19.0 only; version 19.0.1 only; version 19.0.2 only; version 20.0 only; version 20.0.1 only; …
• Mozilla Seamonkey: up to and including 2.20; version 2.0 only; version 2.0.1 only; version 2.0.2 only; version 2.0.3 only; version 2.0.4 only; …
• Mozilla Thunderbird: up to and including 17.0.9; version 17.0 only; version 17.0.1 only; version 17.0.2 only; version 17.0.3 only; version 17.0.4 only; …

Published 2013-09-18. Last modified 2026-06-16.