Firefox <149 Sandbox Escape via Telemetry Boundary Conditions
CVE-2026-4687 Published on March 24, 2026
Sandbox escape due to incorrect boundary conditions in the Telemetry component
Sandbox escape due to incorrect boundary conditions in the Telemetry component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Vulnerability Analysis
CVE-2026-4687 can be exploited with network access, requires 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 Classic Buffer Overflow Vulnerability?
The program copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. A buffer overflow condition exists when a program attempts to put more data in a buffer than it can hold, or when a program attempts to put data in a memory area outside of the boundaries of a buffer. The simplest type of error, and the most common cause of buffer overflows, is the "classic" case in which the program copies the buffer without restricting how much is copied. Other variants exist, but the existence of a classic overflow strongly suggests that the programmer is not considering even the most basic of security protections.
CVE-2026-4687 has been classified to as a Classic Buffer Overflow vulnerability or weakness.
Products Associated with CVE-2026-4687
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Affected Versions
Mozilla Firefox:- Version 115.34, <= 115.* is unaffected.
- 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.