CVE-2026-74987

CRITICAL 9.8CVE-2026-74987 · Published 18/08/2026 · updated 28/10/2026

Package	Affected versions	Patched versions
firefox mozilla	`≥ 141.0, < 153.1.0< 140.14.0`	`153.1.0140.14.0`
thunderbird mozilla	`≥ 141.0, < 153.1.0< 140.14.0`	`153.1.0140.14.0`

Description

Internally found bugs present in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

References

bugzilla.mozilla.org/buglist.cgi · Broken Link
bugzilla.mozilla.org/buglist.cgi · Broken Link
bugzilla.mozilla.org/show_bug.cgi · Permissions Required
mozilla.org/security/advisories/mfsa2026-74 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-76 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-77 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-78 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-79 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-80 · Vendor Advisory

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