Use-after-free in Firefox JS Engine before 149 & ESR <140.9
CVE-2026-4701 Published on March 24, 2026
Use-after-free in the JavaScript Engine component
Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Vulnerability Analysis
CVE-2026-4701 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be critical as this vulnerability has a high impact to the confidentiality, integrity and availability of this component.
Weakness Type
What is a Dangling pointer Vulnerability?
Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.
CVE-2026-4701 has been classified to as a Dangling pointer vulnerability or weakness.
Products Associated with CVE-2026-4701
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Affected Versions
Mozilla Firefox:- Version 140.9, <= 140.* is unaffected.
- Version 149, <= * is unaffected.
- Version 140.9, <= 140.* is unaffected.
- Version 149, <= * is unaffected.
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.