Executive Summary

Memory safety bugs in Firefox 133, Thunderbird 133, Firefox ESR 128.5, and Thunderbird 128.5 could lead to memory corruption and potentially arbitrary code execution. The issue was fixed in the subsequent releases (Firefox 134, ESR 128.6, Thunderbird 134, 128.6). It is not currently listed in the CISA KEV.

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Authoritative CVE Metadata - CVSS Base Score: 5.1 (MEDIUM) - Published: 2025-01-07T16:15:38.973 - Last Modified: 2026-10-05T15:10:00.590

Original Description: Memory safety bugs present in Firefox 133, Thunderbird 133, Firefox ESR 128.5, and Thunderbird 128.5. 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 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.

"Some people are always grumbling because roses have thorns; I am thankful that thorns have roses."

— Alphonse Karr