CVE-2026-5731
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.34%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.34% probability · 27th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-119, CWE-787
- Affected
- mozilla/firefox · mozilla/thunderbird
- Source
- security@mozilla.org
References
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=2021894%2C2022225%2C2022252%2C2022294%2C2023007%2C2023130%2C2023191%2C2023364%2C2023829%2C2024074%2C2024417%2C2024433%2C2024436%2C2024437%2C2024453%2C2024461%2C2024462%2C2024472%2C2024474%2C2024477%2C2025364%2C2025401%2C2025402%2C2025472%2C2026287%2C2026299%2C2026305%2C2026426Broken Link
- 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
- https://access.redhat.com/errata/RHSA-2026:11805
- https://access.redhat.com/errata/RHSA-2026:11813
- https://access.redhat.com/errata/RHSA-2026:12264
- https://access.redhat.com/errata/RHSA-2026:13342
- https://access.redhat.com/errata/RHSA-2026:13412
- https://access.redhat.com/errata/RHSA-2026:13533
- https://access.redhat.com/errata/RHSA-2026:13582
- https://access.redhat.com/errata/RHSA-2026:13583
- https://access.redhat.com/errata/RHSA-2026:13596
- https://access.redhat.com/errata/RHSA-2026:13600
- https://access.redhat.com/errata/RHSA-2026:13665
- https://access.redhat.com/errata/RHSA-2026:13682
- https://access.redhat.com/errata/RHSA-2026:13683
- https://access.redhat.com/errata/RHSA-2026:13922
- https://access.redhat.com/errata/RHSA-2026:13977
- https://access.redhat.com/errata/RHSA-2026:14223
- https://access.redhat.com/errata/RHSA-2026:14303
- https://access.redhat.com/errata/RHSA-2026:15889
- https://access.redhat.com/errata/RHSA-2026:7671
- https://access.redhat.com/errata/RHSA-2026:7672
- https://access.redhat.com/errata/RHSA-2026:8052
- https://access.redhat.com/errata/RHSA-2026:8459
- https://access.redhat.com/errata/RHSA-2026:9345
- https://access.redhat.com/errata/RHSA-2026:9638
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.