CVE-2025-0240

MEDIUM 4.0CVE-2025-0240 · Published 07/01/2025 · updated 05/10/2026

In short

CVE-2025-0240 is a MEDIUM (CVSS 4.0) vulnerability affecting firefox (mozilla), thunderbird (mozilla).
Chance of exploitation in the next 30 days (EPSS): 0.67%, higher than 52.2% of all vulnerabilities.
Fix: update to 128.6.0, 134.0 or later.

Package	Affected versions	Patched versions
firefox mozilla	`< 128.6.0< 134.0`	`128.6.0134.0`
thunderbird mozilla	`≥ 129.0, < 134.0< 128.6.0`	`134.0128.6.0`

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.

References

bugzilla.mozilla.org/show_bug.cgi · Issue Tracking
mozilla.org/security/advisories/mfsa2025-01 · Vendor Advisory
mozilla.org/security/advisories/mfsa2025-02 · Vendor Advisory
mozilla.org/security/advisories/mfsa2025-04 · Vendor Advisory
mozilla.org/security/advisories/mfsa2025-05 · Vendor Advisory
lists.debian.org/debian-lts-announce/2025/01/msg00004.html

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Package

Affected versions

Patched versions

firefox

mozilla

< 128.6.0< 134.0

128.6.0134.0

thunderbird

mozilla

≥ 129.0, < 134.0< 128.6.0

134.0128.6.0

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