CVE-2026-5731
Last modified
CVE-2026-5731 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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. EPSS estimates a 0.34% chance of exploitation in the next 30 days.
Description
Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 149.0.2, Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | 115.34.0 |
| Mozilla | Firefox | 140.9.0 |
| Mozilla | Firefox | 149.0.1 |
| Mozilla | Thunderbird | 140.9.0 |
| Mozilla | Thunderbird | 149.0.1 |
References
- https://www.mozilla.org/security/advisories/mfsa2026-25/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-26/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-27/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-28/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-29/Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
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How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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