CVE-2026-75874 in Firefox
Summary
by MITRE • 08/18/2026
Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 08/18/2026
The identified security issue represents a critical sandbox escape within the Remote Settings Client component of Mozilla Firefox, specifically addressed in version 154. Sandbox escapes are among the most severe classes of vulnerabilities because they allow an attacker to break out of the restricted execution environment imposed by the browser's process isolation model. In modern web browsers, different components such as content processes, GPU processes, and utility processes operate within separate sandboxes with limited privileges to contain potential exploits. When a vulnerability allows escape from this sandbox, it effectively grants the malicious code access to higher-privilege system resources or adjacent memory spaces that were previously protected by operating-level security boundaries.
The Remote Settings Client is responsible for fetching configuration data, such as blocklists and policy settings, from Mozilla servers. This component typically operates with elevated privileges compared to standard web content processes because it needs to modify browser behavior and enforce security policies. If an attacker can trigger a sandbox escape within this specific client, they may achieve arbitrary code execution with the same permissions as the Firefox application itself. This could involve reading sensitive user data, modifying system configurations, or installing persistent malware on the host machine, depending on the operating environment and current privilege levels of the browser process.
From an industry standard perspective, this vulnerability aligns closely with CWE-270, which describes a Privilege Context Mismatch leading to a Sandbox Escape. It also maps to MITRE ATT&CK techniques related to Defense Evasion and Command and Control, specifically those involving container or sandbox escape mechanisms such as T1615. The exploitation of this flaw would likely require an attacker to craft malicious content that interacts with the Remote Settings API in a way that triggers the underlying memory corruption or logic error responsible for the boundary breach. This could involve manipulating specific data structures or triggering race conditions during the processing of remote configuration updates.
The operational impact of such a vulnerability is significant, as it undermines one of the primary defense-in-depth strategies employed by web browsers: process isolation. Without effective sandboxing, a single compromised webpage or extension can potentially take control of the entire browser session and, in some cases, interact with the underlying operating system. This elevates the risk from simple data theft to full system compromise, allowing for broader lateral movement within a network if the user is part of an enterprise environment where Firefox is deployed as the standard client.
Mitigation strategies primarily involve applying the vendor-provided patch included in Firefox 154 immediately across all affected systems. For organizations managing large fleets of browsers, automated deployment tools should be utilized to ensure rapid distribution of this update. Additionally, administrators can enforce policies that restrict the execution of unsigned extensions or disable certain remote settings features if they are not strictly necessary for business operations, thereby reducing the attack surface. Continuous monitoring for anomalous process behavior and ensuring that endpoint detection and response solutions are configured to alert on unexpected privilege escalations within browser processes provide an additional layer of defense against exploitation attempts while patching is being implemented.