CVE-2026-100762 in Firefox
Summary
by MITRE • 09/29/2026
Sandbox escape due to use-after-free in the DOM: Content Processes component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
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Analysis
by VulDB Data Team • 09/29/2026
The identified vulnerability represents a critical security flaw within the Mozilla Firefox browser ecosystem, specifically located in the Content Processes component responsible for handling Document Object Model operations. This issue is classified as an use-after-free error, which occurs when software continues to use memory that has already been freed or deallocated by the system. In the context of web browsers, such vulnerabilities are particularly dangerous because they can allow maliciously crafted content on a webpage to exploit the browser's internal state management mechanisms. When a pointer references a previously allocated block of memory after it has been released but before it is reallocated for another purpose, the application may read or write data based on stale assumptions about that memory region. This discrepancy creates an opportunity for attackers to manipulate how the browser interprets subsequent operations, potentially leading to arbitrary code execution within the context of the compromised process.
From a technical perspective, this specific flaw falls under the Common Weakness Enumeration category CWE-416, which defines use-after-free conditions as a significant source of instability and security breaches. The exploitation vector typically involves triggering a sequence of DOM manipulations that cause the browser to free an object while retaining references to it elsewhere in memory. An attacker could construct a malicious webpage containing JavaScript code designed to force this race condition or logical error, thereby gaining control over the freed memory's contents. By carefully crafting input data, the adversary can overwrite critical function pointers or vtables within the Content Process, effectively hijacking the execution flow of the browser engine. This capability is severe because it bypasses many standard sandboxing protections that rely on process isolation to contain damage from compromised web content.
The operational impact of this vulnerability extends beyond simple application crashes or denial of service scenarios. Successful exploitation allows for a sandbox escape, meaning an attacker can break out of the restricted environment where untrusted web pages are executed and gain higher privileges within the operating system. This aligns with several techniques observed in the MITRE ATT&CK framework, particularly those related to privilege escalation and defense evasion through memory corruption. Once inside the Content Process, further exploitation steps could lead to full system compromise, including data exfiltration, installation of persistent malware, or lateral movement across a network if the user has administrative rights. The severity is amplified by the widespread adoption of Firefox as a primary web browser for both enterprise and individual users, making this a high-impact target for cybercriminals seeking initial access vectors through social engineering or drive-by downloads.
To mitigate the risks associated with this vulnerability, organizations must ensure that all instances of Mozilla Firefox are updated to the patched versions immediately. The specific releases addressing this issue include Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. For enterprise environments utilizing Extended Support Release channels, IT administrators should verify that automatic update policies are enabled to prevent users from remaining on vulnerable versions for extended periods. Additionally, implementing application whitelisting or strict content security policies can help reduce the attack surface by preventing the execution of unauthorized scripts or limiting interactions with untrusted domains until patches are fully deployed across all endpoints. Regular vulnerability scanning and patch management cycles remain essential defenses against such memory corruption flaws that continue to plague complex software architectures like modern web browsers.