What’s Vulnerable › Vulnerabilities

CVE-2025-8027: JavaScript engine only wrote partial return value to stack

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-07-22 · updated 2026-10-05
• Weakness: CWE-457

Description

On 64-bit platforms IonMonkey-JIT only wrote 32 bits of the 64-bit return value space on the stack. Baseline-JIT, however, read the entire 64 bits. This vulnerability was fixed in Firefox 141, Firefox ESR 115.26, Firefox ESR 128.13, Firefox ESR 140.1, Thunderbird 141, Thunderbird 128.13, and Thunderbird 140.1.

Affected products

• Mozilla Firefox: before 115.26.0; before 141.0; from 128.0 before 128.13.0; from 140.0 before 140.1.0 — fixed in 115.26.0, 128.13.0, 140.1.0, 141.0
• Mozilla Thunderbird: before 128.13.0; before 141.0; from 140.0 before 140.1.0 — fixed in 128.13.0, 140.1.0, 141.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 115.26.0, 128.13.0, 140.1.0, 141.0; Mozilla Thunderbird 128.13.0, 140.1.0, 141.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1968423
• https://www.mozilla.org/security/advisories/mfsa2025-56/
• https://www.mozilla.org/security/advisories/mfsa2025-57/
• https://www.mozilla.org/security/advisories/mfsa2025-58/
• https://www.mozilla.org/security/advisories/mfsa2025-59/
• https://www.mozilla.org/security/advisories/mfsa2025-61/
• https://www.mozilla.org/security/advisories/mfsa2025-62/
• https://www.mozilla.org/security/advisories/mfsa2025-63/
• https://lists.debian.org/debian-lts-announce/2025/07/msg00016.html

Get alerted when CVE-2025-8027 or the next vulnerability affects your stack