What’s Vulnerable › Vulnerabilities

CVE-2025-0240: Compartment mismatch when parsing JavaScript JSON module

• Severity: medium (CVSS 4.0 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-01-07 · updated 2026-10-05
• Weakness: CWE-416

Description

Parsing a JavaScript module as JSON could, under some circumstances, cause cross-compartment access, which may result in a use-after-free. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.

Affected products

• Mozilla Firefox: before 128.6.0; before 134.0 — fixed in 128.6.0, 134.0
• Mozilla Thunderbird: before 128.6.0; from 129.0 before 134.0 — fixed in 128.6.0, 134.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 128.6.0, 134.0; Mozilla Thunderbird 128.6.0, 134.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1929623
• https://www.mozilla.org/security/advisories/mfsa2025-01/
• https://www.mozilla.org/security/advisories/mfsa2025-02/
• https://www.mozilla.org/security/advisories/mfsa2025-04/
• https://www.mozilla.org/security/advisories/mfsa2025-05/
• https://lists.debian.org/debian-lts-announce/2025/01/msg00004.html

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