CVE-2025-4087: Mozilla Firefox

Medium severity, CVSS 4.8. EPSS: 0.3% chance of exploitation in the next 30 days.

A vulnerability was identified in Thunderbird where XPath parsing could trigger undefined behavior due to missing null checks during attribute access. This could lead to out-of-bounds read access and potentially, memory corruption. This vulnerability was fixed in Firefox 138, Firefox ESR 128.10, Thunderbird 138, and Thunderbird 128.10.

Affected products

• Mozilla Firefox: before 128.10 (fixed in 128.10); before 138.0 (fixed in 138.0)
• Mozilla Thunderbird: before 128.10.0 (fixed in 128.10.0); before 138.0 (fixed in 138.0)

Published 2025-04-29. Last modified 2026-10-05.