CVE-2016-5259: Mozilla Firefox

High severity, CVSS 8.8. EPSS: 3.3% chance of exploitation in the next 30 days.

Use-after-free vulnerability in the CanonicalizeXPCOMParticipant function in Mozilla Firefox before 48.0 and Firefox ESR 45.x before 45.3 allows remote attackers to execute arbitrary code via a script that closes its own Service Worker within a nested sync event loop.

Affected products

• Mozilla Firefox: up to and including 47.0.1; version 45.1.0 only; version 45.1.1 only; version 45.2.0 only; version 45.3.0 only
• Oracle Linux: version 5.0 only; version 6 only; version 7 only

Published 2016-08-05. Last modified 2026-06-17.