Memory Safety Bugs in Firefox 146 & Thunderbird 146
CVE-2026-0891 Published on January 13, 2026
Memory safety bugs fixed in Firefox ESR 140.7, Thunderbird ESR 140.7, Firefox 147 and Thunderbird 147
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 affects Firefox < 147, Firefox ESR < 140.7, Thunderbird < 147, and Thunderbird < 140.7.
Vulnerability Analysis
CVE-2026-0891 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.
Weakness Type
What is a Buffer Overflow Vulnerability?
The software performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer.
CVE-2026-0891 has been classified to as a Buffer Overflow vulnerability or weakness.
Products Associated with CVE-2026-0891
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Affected Versions
Mozilla Firefox:- Version unspecified and below 147 is affected.
- Version unspecified and below 140.7 is affected.
- Version unspecified and below 147 is affected.
- Version unspecified and below 140.7 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.