CVE-2026-6786
High
Description
Memory safety bugs present in Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149. 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 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
SeverityHigh
CVSS7.5
Exploit probability—
Product
Mozilla Firefox
PublishedApr 26, 2026
First seenApr 26, 2026
How to fix
Update
- mozilla firefox150.0, 140.10.0 or later
- mozilla thunderbird140.10.0 or later
Vendor advisories
- access.redhat.com/errata/RHSA-2026:19704
- access.redhat.com/errata/RHSA-2026:17690
- access.redhat.com/errata/RHSA-2026:19463
- access.redhat.com/errata/RHSA-2026:10767
- access.redhat.com/errata/RHSA-2026:12285
- access.redhat.com/errata/RHSA-2026:19041
- access.redhat.com/errata/RHSA-2026:19131
- access.redhat.com/errata/RHSA-2026:10766
- access.redhat.com/errata/RHSA-2026:13537
- access.redhat.com/errata/RHSA-2026:19655
- access.redhat.com/errata/RHSA-2026:19465
- access.redhat.com/errata/RHSA-2026:19542
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mozilla firefox | v < 150.0, 140.0 ≤ v < 140.10.0 | 150.0, 140.10.0 |
| mozilla thunderbird | 140.0 ≤ v < 140.10.0 | 140.10.0 |
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