CVE-2026-12294
CRITICAL 9.6Sandbox escape in the DOM: Workers component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.
ELEVATED IMPACT
Severe if exploited (CVSS 9.6), but no known exploitation and low modeled probability. Patch on a normal cadence.
Exploitation likelihood
0.4%chance of exploitation in 30 days · 28th percentile
○ In CISA KEV
○ Public exploit / PoC
Impact if exploited
9.6CVSS 3.1 · CRITICAL
- ConfidentialityHigh
- IntegrityHigh
- AvailabilityHigh
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-693
- CWE-266
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
References
Advisories
Technical & other
- https://bugzilla.mozilla.org/show_bug.cgi?id=2039873
- 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-2026-12294
- https://bugzilla.redhat.com/show_bug.cgi?id=2489207
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12294.json