CVE-2026-8947

HIGH 7.3CVE-2026-8947 · Published 19/05/2026 · updated 14/10/2026

In short

CVE-2026-8947 is a HIGH (CVSS 7.3) vulnerability affecting firefox (mozilla), thunderbird (mozilla).
Chance of exploitation in the next 30 days (EPSS): 0.41%, higher than 35.7% of all vulnerabilities.
Fix: update to 140.11.0, 115.36.0, 151.0.0, 140.11 or later.

Package	Affected versions	Patched versions
firefox mozilla	`≥ 140.0, < 140.11.0< 115.36.0< 151.0.0`	`140.11.0115.36.0151.0.0`
thunderbird mozilla	`< 140.11`	`140.11`

Description

Use-after-free in the DOM: Bindings (WebIDL) component. This vulnerability was fixed in Firefox 151, Firefox ESR 115.36, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

References

bugzilla.mozilla.org/show_bug.cgi · Permissions Required
mozilla.org/security/advisories/mfsa2026-46 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-47 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-48 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-50 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-51 · Vendor Advisory
access.redhat.com/errata/RHSA-2026:21378
access.redhat.com/errata/RHSA-2026:21380
access.redhat.com/errata/RHSA-2026:21381
access.redhat.com/errata/RHSA-2026:21382
access.redhat.com/errata/RHSA-2026:22325
access.redhat.com/errata/RHSA-2026:22643
access.redhat.com/errata/RHSA-2026:26174

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