CVE-2026-4721CRITICAL 9.8EPSS p34.3%
CVE-2026-4721CVE-2026-4721
Description
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 was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Scoring
| CVSS 3.1 | 9.8 (CRITICAL) |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| EPSS | 0.43% probability of exploitation · percentile 34.3% · 2026-06-18T12:00:27Z |
| Published | 2026-03-24 |
| Last modified | 2026-04-13 |
Underlying weaknesses· 1
References
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=2013762%2C2015291%2C2016591%2C2016661%2C2016664%2C2017303%2C2017894%2C2018090%2C2018196%2C2018379%2C2019112%2C2022090%2C2022243%2C2022351%2C2022478%2C2022676
- https://www.mozilla.org/security/advisories/mfsa2026-20/
- https://www.mozilla.org/security/advisories/mfsa2026-21/
- https://www.mozilla.org/security/advisories/mfsa2026-22/
- https://www.mozilla.org/security/advisories/mfsa2026-23/
- https://www.mozilla.org/security/advisories/mfsa2026-24/
1
| Type | Target | Confidence | Tier |
|---|---|---|---|
| Weakness | Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')cwe-120 | 0% | live |
Related by meaning· 6
Nearest entities by semantic similarity across the cs-graph corpus.