CVE-2013-5596: Mozilla Firefox

Medium severity, CVSS 6.8. EPSS: 3.1% chance of exploitation in the next 30 days.

The cycle collection (CC) implementation in Mozilla Firefox before 25.0, Firefox ESR 24.x before 24.1, Thunderbird before 24.1, and SeaMonkey before 2.22 does not properly determine the thread for release of an image object, which allows remote attackers to execute arbitrary code or cause a denial of service (race condition and application crash) via a large HTML document containing IMG elements, as demonstrated by the Never-Ending Reddit on reddit.com.

Affected products

• Mozilla Firefox: version 24.0 only; version 24.0.1 only; version 24.0.2 only; up to and including 24.0; version 19.0 only; version 19.0.1 only; …
• Mozilla Seamonkey: up to and including 2.22; 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 24.0.1; version 17.0 only; version 17.0.1 only; version 17.0.2 only; version 17.0.3 only; version 17.0.4 only; …
• Mozilla Thunderbird ESR: version 17.0.9 only

Published 2013-10-30. Last modified 2026-06-16.