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.
Severity
CVSS 3.0
8.8 high
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS
3.3% chance of exploitation in the next 30 days; higher than 88% of CVEs (scores of 2026-10-31)