CVE-2026-117962 in Firefox
Summary
by MITRE • 10/27/2026
Sandbox escape due to incorrect boundary conditions in the Storage: Quota Manager component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/27/2026
The identified security flaw resides within the Storage Quota Manager component of Mozilla Firefox, representing a critical sandbox escape vector caused by incorrect boundary condition handling. In modern web browsers, the browser engine operates as a complex multi-process architecture where untrusted content from websites runs in isolated sandboxes to prevent malicious actors from accessing sensitive system resources or user data. The storage subsystem is particularly sensitive because it manages persistent local data such as cookies, cache files, and IndexedDB entries, which are subject to strict quota limits enforced by the browser's security model. When boundary conditions within this manager are not correctly validated, an attacker can manipulate these limits to exceed allocated memory or file system quotas in unintended ways. This miscalculation allows for buffer overflows or logic errors that bypass the intended isolation boundaries between the untrusted web content and the trusted browser processes.
From a technical perspective, the vulnerability exploits how the Quota Manager calculates and enforces storage constraints during read and write operations. If an attacker can trigger specific sequences of storage allocations with carefully crafted inputs, they may cause the application to misinterpret memory addresses or file offsets due to off-by-one errors or integer overflows inherent in improper boundary checks. This flaw effectively breaks the sandbox isolation model, which is fundamental to browser security. By escaping the sandbox, a malicious script executed within a compromised webpage could gain elevated privileges, potentially allowing it to execute arbitrary code on the host operating system with the same permissions as the user running the browser. Such an escape transforms what would typically be a cross-site scripting or content injection issue into a full remote code execution vulnerability, significantly increasing its severity and potential for exploitation in targeted attacks.
The operational impact of this vulnerability is severe due to its nature as a sandbox escape. Successful exploitation could allow threat actors to install malware, steal sensitive credentials stored locally by the browser, access private user data such as emails or financial records, or use the compromised machine as part of a botnet. Because storage operations are frequent and often occur in response to normal browsing activities like loading pages with heavy local state requirements, this vulnerability could be triggered without requiring complex social engineering beyond convincing a victim to visit a maliciously crafted website that leverages specific storage APIs. The risk is compounded by the fact that many enterprise environments rely on browsers for secure access to internal applications, making such an escape particularly dangerous in corporate networks where lateral movement might follow initial compromise.
To mitigate this risk, users must ensure they are running Firefox version 159 or later, as well as any affected versions of Firefox ESR updated to patch level 153.6 or higher. These updates contain the necessary code corrections that enforce strict boundary checks within the Storage Quota Manager, preventing the miscalculation of storage limits and ensuring proper isolation between processes. Organizations should prioritize deploying these patches across all endpoints using automated vulnerability management tools to minimize exposure windows. Additionally, security teams should monitor for indicators of compromise related to unusual browser behavior or unexpected network connections originating from Firefox processes, as attackers may attempt to exploit this flaw before widespread patching occurs. Adhering to the principle of least privilege by running browsers with restricted user accounts can also reduce the impact if a sandbox escape were to occur in unpatched systems.
This vulnerability aligns with Common Weakness Enumeration (CWE) categories such as CWE-190, which describes integer overflow or wraparound errors that lead to buffer overflows, and CWE-20, which covers improper input validation leading to boundary condition failures. In the context of the MITRE ATT&CK framework, this flaw facilitates techniques associated with Defense Evasion by allowing attackers to bypass sandbox protections, specifically relating to process injection or arbitrary code execution within trusted processes. Understanding these classifications helps security professionals categorize the threat accurately and apply appropriate detection rules based on known exploitation patterns for similar browser vulnerabilities. Continuous monitoring of vendor advisories and maintaining up-to-date software configurations remain essential defenses against such sophisticated web-based attack vectors.