CVE-2026-12299
MEDIUM 5.4JIT miscompilation in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
NO EXPLOITATION SIGNALS
No known exploitation, public exploit, or elevated probability at this time. Track for changes.
Exploitation likelihood
0.3%chance of exploitation in 30 days · 22nd percentile
○ In CISA KEV
○ Public exploit / PoC
Impact if exploited
5.4CVSS 3.1 · MEDIUM
- ConfidentialityLow
- IntegrityLow
- AvailabilityNone
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ✓Privileges: No account or privileges required
- ⚠User interaction: A user must take an action (click / open a file)
- ✓Complexity: No special conditions — reliably repeatable
✓ lowers the bar for an attacker · ⚠ raises it
Affected
Products Firefox Thunderbird Red Hat Enterprise Linux Appstream (V. 10) Red Hat Enterprise Linux Appstream (V. 8) Red Hat Enterprise Linux Appstream (V. 9) Red Hat Enterprise Linux 10 Red Hat Enterprise Linux 6 Red Hat Enterprise Linux 7
Weakness (CWE)
- CWE-843
- CWE-733
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
References
Advisories
Technical & other
- https://bugzilla.mozilla.org/show_bug.cgi?id=2043139
- https://www.mozilla.org/security/advisories/mfsa2026-57/
- https://www.mozilla.org/security/advisories/mfsa2026-58/
- https://www.mozilla.org/security/advisories/mfsa2026-59/
- https://www.mozilla.org/security/advisories/mfsa2026-60/
- https://www.mozilla.org/security/advisories/mfsa2026-61/
- https://access.redhat.com/security/cve/CVE-2026-12299
- https://bugzilla.redhat.com/show_bug.cgi?id=2489212
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12299.json