The nsScannerString::AppendUnicodeTo function in Mozilla Firefox before 45.0 and Firefox ESR 38.x before 38.7 does not verify that memory allocation succeeds, which allows remote attackers to execute arbitrary code or cause a denial of service (out-of-bounds read) via crafted Unicode data in an HTML, XML, or SVG document.
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
3.0% chance of exploitation in the next 30 days; higher than 87% of CVEs (scores of 2026-10-31)