CVE-2026-92066 in Firefox
Summary
by MITRE • 09/15/2026
Sandbox escape in the Profile Backup component. This vulnerability was fixed in Firefox 156.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 09/15/2026
The discovery of a sandbox escape within the Profile Backup component of Mozilla Firefox represents a critical security failure that undermines one of the primary defense-in-depth mechanisms employed by modern web browsers. The browser process sandbox is designed to restrict the privileges of code executing untrusted content, such as JavaScript from websites or plugins, preventing malicious actors from accessing sensitive system resources or user data even if they successfully exploit an initial vulnerability in the rendering engine. When this isolation boundary fails due to a flaw in how backup operations are handled, it allows potentially hostile code executed within the browser's restricted environment to break out and execute commands with higher privileges on the host operating system. This specific weakness was addressed in Firefox version 156, marking a significant step toward restoring the integrity of the security model for users relying on this widely used web client.
From a technical perspective, vulnerabilities classified as sandbox escapes typically stem from improper validation of inputs passed to native code or incorrect handling of inter-process communication channels that bridge the gap between low-privilege and high-privilege processes. In the context of profile backup operations, the browser likely interacts with file system APIs to archive user data such as bookmarks, history, passwords, and extension settings. If the implementation fails to properly sanitize paths, handles, or memory structures during this archival process, an attacker could craft a malicious webpage that triggers specific conditions within the backup routine. By exploiting race conditions, buffer overflows, or logic errors in how these files are processed before being written to disk, the attacker can manipulate the execution flow to bypass sandbox restrictions. This effectively grants arbitrary code execution capabilities outside the confined browser environment, allowing access to local file systems, network interfaces, and other sensitive system components that should remain inaccessible from web content.
The operational impact of such a vulnerability is severe, as it transforms what might otherwise be a contained cross-site scripting or memory corruption issue into a full remote code execution scenario. An attacker who can trick a user into visiting a specially crafted website could leverage this flaw to install malware, steal sensitive credentials stored in the browser profile, monitor keystrokes, or use the compromised machine as part of a botnet. Since Firefox is often used for banking and accessing corporate resources, the breach of sandbox isolation poses a direct threat to financial security and organizational data integrity. The fact that this issue persisted until version 156 indicates that while automated testing and fuzzing are effective at catching many memory safety issues, complex interactions between browser components like backup utilities and the core rendering engine can still slip through initial review processes if specific edge cases involving file system operations are not thoroughly tested under sandboxed conditions.
To mitigate risks associated with similar vulnerabilities in Firefox and other browsers, users should ensure they are running the latest stable release where such patches have been applied. Regular updates are critical because vendors continuously refine their security models based on emerging threat intelligence and discovered attack vectors. Additionally, employing browser extensions that restrict permissions or limit access to local resources can provide an additional layer of defense. From a development standpoint, adhering strictly to secure coding practices for file I/O operations is essential. This includes validating all input paths against directory traversal attacks, ensuring proper permission checks before writing files, and minimizing the attack surface by reducing the functionality exposed within sandboxed processes. Security teams should also prioritize fuzz testing specifically targeting backup and profile management components to identify logic errors that standard memory safety tools might miss.
This incident aligns with common vulnerability classifications found in industry standards such as CWE-250, which covers execution with unnecessary privileges, and CWE-787, relating to out-of-bounds writes that can lead to arbitrary code execution when combined with sandbox bypass techniques. In the context of the MITRE ATT&CK framework, this type of exploit falls under T1068 Exploitation for Privilege Escalation, where an adversary leverages a software vulnerability to gain elevated access on a system. Understanding these mappings helps security professionals categorize the severity and potential impact more accurately during incident response planning. The resolution in Firefox 156 serves as a reminder that even well-established browsers require constant vigilance against sophisticated attacks targeting core infrastructure components like profile management, which hold keys to significant amounts of user identity data.