CVE-2023-4577: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 0.7% chance of exploitation in the next 30 days.

When `UpdateRegExpStatics` attempted to access `initialStringHeap` it could already have been garbage collected prior to entering the function, which could potentially have led to an exploitable crash. This vulnerability affects Firefox < 117, Firefox ESR < 115.2, and Thunderbird < 115.2.

Affected products

• Mozilla Firefox: before 117.0 (fixed in 117.0)
• Mozilla Firefox ESR: before 115.2 (fixed in 115.2)
• Mozilla Thunderbird: before 115.2 (fixed in 115.2)

Published 2023-09-11. Last modified 2026-06-17.