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CVE PROGRAM SOURCE RECORD9.8 Critical

CVE-2026-4720

Memory safety bugs fixed in Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149

Description

Memory safety bugs present in Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Mozilla Firefox

  • 140.9 to ≤ 140.*unaffected
  • 149 to ≤ *unaffected

Mozilla Thunderbird

  • 140.9 to ≤ 140.*unaffected
  • 149 to ≤ *unaffected

References