CVE-2016-5270: Mozilla Firefox

Critical severity, CVSS 9.8. EPSS: 4% chance of exploitation in the next 30 days.

Heap-based buffer overflow in the nsCaseTransformTextRunFactory::TransformString function in Mozilla Firefox before 49.0, Firefox ESR 45.x before 45.4, and Thunderbird < 45.4 allows remote attackers to cause a denial of service (boolean out-of-bounds write) or possibly have unspecified other impact via Unicode characters that are mishandled during text conversion.

Affected products

• Mozilla Firefox: up to and including 48.0.2; version 45.1.0 only; version 45.1.1 only; version 45.2.0 only; version 45.3.0 only

Published 2016-09-22. Last modified 2026-06-17.