CVE-2026-117868 in Firefox
Summary
by MITRE • 10/27/2026
Sandbox escape in the DOM: Networking component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.
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Analysis
by VulDB Data Team • 10/28/2026
The disclosed security issue represents a critical sandbox escape within the Document Object Model networking components of Mozilla Firefox browsers. This type of vulnerability typically arises from improper isolation between privileged browser processes and untrusted web content, allowing malicious scripts executed in a standard tab context to break out into higher-privilege environments. In modern browser architectures, such as Gecko used by Firefox, various subsystems operate with elevated privileges to handle sensitive operations like network requests, file system access, or inter-process communication. When the sandboxing mechanisms fail due to logic errors or missing validation checks in these networking components, an attacker can leverage this flaw to execute arbitrary code outside the intended security boundary.
The technical root cause likely involves a failure in enforcing strict origin isolation or permission boundaries within the DOM API surface area responsible for handling network data. Attackers could craft specific HTML and JavaScript payloads that trigger unintended behavior during asynchronous network operations or resource loading sequences. By exploiting race conditions, type confusion errors, or improper state management within these components, malicious actors can bypass security restrictions such as Content Security Policy (CSP) directives or same-origin policies. This escape allows the attacker to access sensitive browser internals, potentially leading to full system compromise if combined with other local exploitation techniques.
From an operational perspective, this vulnerability poses a severe risk to users browsing untrusted websites or visiting pages containing malicious advertisements and third-party scripts. Successful exploitation could result in unauthorized data exfiltration, session hijacking, installation of persistent malware, or further lateral movement within the user's network environment. The impact is particularly acute because it undermines one of the primary defenses against web-based attacks: the browser sandbox. Without this protection, even simple drive-by download attempts become significantly more dangerous as they can escalate privileges to interact with local system resources directly.
To mitigate these risks, users must ensure their browsers are updated immediately to Firefox version 159 or later, including specific maintenance releases like Firefox ESR 115.44 and Firefox ESR 153.6 where applicable for enterprise environments. Organizations should enforce automatic update policies across all endpoints to minimize exposure windows. Additionally, implementing robust Content Security Policy headers on web applications can provide an additional layer of defense by restricting the types of scripts that can execute within browser contexts. Monitoring network traffic for anomalous behavior originating from browser processes may also aid in detecting attempted exploitation activities before they result in full compromise.
This vulnerability aligns with Common Weakness Enumeration categories such as CWE-250, which describes execution with unnecessary privileges, and CWE-94, relating to code injection flaws that allow attackers to inject malicious commands into web applications. In the context of MITRE ATT&CK techniques, this flaw facilitates initial access through browser exploitation (T1189) and potentially enables privilege escalation if the sandbox escape leads to higher-level system interactions. The remediation strategy focuses on patching the underlying code logic that fails to properly validate inputs or enforce process boundaries within the networking stack of the DOM implementation.