CVE-2025-1933: Mozilla Firefox

High severity, CVSS 7.6. EPSS: 0.3% chance of exploitation in the next 30 days.

On 64-bit CPUs, when the JIT compiles WASM i32 return values they can pick up bits from left over memory. This can potentially cause them to be treated as a different type. This vulnerability was fixed in Firefox 136, Firefox ESR 115.21, Firefox ESR 128.8, Thunderbird 136, and Thunderbird 128.8.

Affected products

• Mozilla Firefox: before 115.21.0 (fixed in 115.21.0); before 136.0 (fixed in 136.0); from 116.0, before 128.8.0 (fixed in 128.8.0)
• Mozilla Thunderbird: before 128.8 (fixed in 128.8); from 129.0, before 136.0 (fixed in 136.0)

Published 2025-03-04. Last modified 2026-10-05.