Memory Safety Bug in Firefox (ESR 115.33/140.8 & 148) prior to v149
CVE-2026-4721 Published on March 24, 2026
Memory safety bugs fixed in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149
Memory safety bugs present in Firefox ESR 115.33, 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 affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Products Associated with CVE-2026-4721
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Affected Versions
Mozilla Firefox:- Version unspecified and below 149 is affected.
- Version unspecified and below 115.34 is affected.
- Version unspecified and below 140.9 is affected.
- Version unspecified and below 149 is affected.
- Version unspecified and below 140.9 is affected.