CVE-2017-5456 in Firefox
Summary
by MITRE
A mechanism to bypass file system access protections in the sandbox using the file system request constructor through an IPC message. This allows for read and write access to the local file system. This vulnerability affects Firefox ESR < 52.1 and Firefox < 53.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability identified as CVE-2017-5456 represents a critical sandbox escape mechanism within Mozilla Firefox that undermines the browser's security model through improper handling of inter-process communication messages. This flaw specifically targets the file system access controls implemented in Firefox's sandboxing architecture, creating a pathway for malicious actors to circumvent protective boundaries that are fundamental to preventing unauthorized file system operations. The vulnerability exists in the way Firefox processes file system requests through the IPC (Inter-Process Communication) messaging system, where the file system request constructor fails to properly validate or enforce access restrictions that should normally be maintained between different process contexts. This issue affects both Firefox Extended Support Release versions prior to 52.1 and standard Firefox releases before version 53, indicating a widespread impact across multiple browser variants.
The technical implementation of this vulnerability stems from insufficient input validation within the sandboxed environment's file system request handling mechanism. When Firefox processes file system operations through IPC messages, the system fails to properly validate the parameters passed through these messages, allowing attackers to construct malicious requests that bypass normal file system access controls. The flaw specifically manifests in how the file system request constructor interprets and executes IPC messages, enabling unauthorized read and write operations on the local file system without proper authorization checks. This represents a classic sandbox bypass vulnerability where the protective isolation between different browser processes is compromised, allowing code execution with elevated privileges that should normally be restricted.
The operational impact of CVE-2017-5456 is severe and potentially devastating for affected systems, as it provides attackers with unrestricted access to the local file system through the browser's sandboxed environment. Successful exploitation could enable attackers to read sensitive files, modify system configurations, install malware, or exfiltrate data without detection. The vulnerability essentially allows for arbitrary file system access that bypasses the fundamental security boundaries that protect users from malicious code execution. This type of vulnerability is particularly dangerous in targeted attacks where attackers seek to establish persistent access or escalate privileges within compromised systems, as it provides a direct pathway to system-level operations that would normally require more complex exploitation techniques.
From a cybersecurity perspective, this vulnerability aligns with CWE-284 (Improper Access Control) and represents a specific instance of privilege escalation through sandbox bypass mechanisms. The ATT&CK framework categorizes this vulnerability under T1059 (Command and Scripting Interpreter) and T1070 (Indicator Removal on Host) as attackers could leverage the file system access to execute malicious commands and subsequently cover their tracks. Organizations should prioritize immediate patching of affected Firefox installations to prevent exploitation, as the vulnerability provides direct access to system resources that could be used for data exfiltration, system compromise, or lateral movement within networks. The remediation process involves updating to Firefox versions 52.1 ESR or 53.0 and later, which include the necessary fixes to properly validate file system request parameters and maintain proper sandbox boundaries. Additionally, organizations should consider implementing network monitoring to detect potential exploitation attempts and maintain updated threat intelligence feeds to identify any attempts to leverage this vulnerability in the wild.