CVE-2026-0891
High
Description
Memory safety bugs present in Firefox ESR 140.6, Thunderbird ESR 140.6, Firefox 146 and Thunderbird 146. 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 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.
SeverityHigh
CVSS8.1
Exploit probability—
Product
Mozilla Firefox
PublishedJan 13, 2026
First seenJan 13, 2026
Weakness typeCWE-119Memory buffer bounds error
How to fix
Update
- mozilla firefox140.7.0, 147.0 or later
- mozilla thunderbird140.7.0, 147.0 or later
Vendor advisories
- access.redhat.com/errata/RHSA-2026:2231
- access.redhat.com/errata/RHSA-2026:2271
- access.redhat.com/errata/RHSA-2026:2286
- access.redhat.com/errata/RHSA-2026:0667
- access.redhat.com/errata/RHSA-2026:2220
- access.redhat.com/errata/RHSA-2026:2074
- access.redhat.com/errata/RHSA-2026:1471
- access.redhat.com/errata/RHSA-2026:2073
- access.redhat.com/errata/RHSA-2026:1461
- access.redhat.com/errata/RHSA-2026:2070
- access.redhat.com/errata/RHSA-2026:1487
- access.redhat.com/errata/RHSA-2026:2069
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 140.7.0, v < 147.0 | 140.7.0, 147.0 |
| mozilla thunderbird | v < 140.7.0, v < 147.0 | 140.7.0, 147.0 |
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