CVE-2026-0891

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-01-13 14:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-07-15 02:17 UTC Last updatedMost recent change to the record

Details

Published

2026-01-13 14:16 UTC

Last modified

2026-07-15 02:17 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-119 · Buffer errors

Record status

Modified

Affected

• Mozilla Firefox < 140.7.0
• Mozilla Firefox < 147.0
• Mozilla Thunderbird < 140.7.0
• Mozilla Thunderbird < 147.0

Attack profile CVSS 3.1 · 8.1

Attack vector

Network

Complexity

High

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High