🛡️ CVE-2025-0240 on Debian — firefox-esr
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.
Distribution advisory
This page covers CVE-2025-0240 as tracked by Debian, for the package firefox-esr. The fix is available in version 128.6.0esr-1; earlier versions remain affected.
How this vulnerability can be exploited
This issue can be reached with local access to the system, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity low, availability none.
Weakness class
DEBIAN-CVE-2025-0240 is classified as CWE-416: Use After Free. Memory is used after being released, so its contents may already belong to something else.
Affected software
DEBIAN-CVE-2025-0240 is recorded against 2 packages.
- firefox-esr (fixed in 128.6.0esr-1)
- thunderbird (fixed in 1:128.6.0esr-1)
Timeline and source
Published on 7 January 2025 and last revised on 4 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.
References
CVE-2025-0240 on other distributions
Each distribution ships its own build and its own fixed version. Pick the one you run:
Details
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Affected Packages
| Software | From version | Fixed in |
|---|---|---|
| firefox-esr | — | 128.6.0esr-1 |
| thunderbird | — | 1:128.6.0esr-1 |
References
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Vulnerability Monitoring
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