CVE-2018-5107 in Firefox
Summary
by MITRE
The printing process can bypass local access protections to read files available through symlinks, bypassing local file restrictions. The printing process requires files in a specific format so arbitrary data cannot be read but it is possible that some local file information could be exposed. This vulnerability affects Firefox < 58.
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Analysis
by VulDB Data Team • 02/01/2021
The vulnerability identified as CVE-2018-5107 represents a significant security flaw in the Firefox browser's printing functionality that allows unauthorized file access through symbolic link manipulation. This issue specifically targets the printing process which is designed to handle files in particular formats but inadvertently creates an avenue for information disclosure through symlink traversal attacks. The vulnerability exists within the local file access controls that are meant to prevent unauthorized reading of system files, yet the printing subsystem fails to properly validate symbolic link paths before processing them. The flaw affects Firefox versions prior to 58, indicating that this was a known issue that required remediation through browser updates and patches.
The technical implementation of this vulnerability stems from inadequate path validation within Firefox's printing subsystem. When the browser processes print jobs, it accesses files through a specific workflow that includes handling symbolic links, but the validation logic does not sufficiently check whether these symbolic links point to restricted local files. This creates a scenario where an attacker could potentially craft a print job that references sensitive files through symbolic links, thereby bypassing the intended local access protections. The vulnerability operates under the principle that while the printing process requires files in specific formats, the symbolic link resolution mechanism allows for information exposure even when arbitrary data cannot be directly read. This aligns with CWE-22 which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal attacks. The attack vector specifically targets the file system access controls that are fundamental to preventing unauthorized access to local resources.
The operational impact of CVE-2018-5107 extends beyond simple information disclosure, as it represents a potential escalation path for attackers who may have already gained some level of system access. Although the vulnerability does not allow for arbitrary data reading, the exposure of local file information could provide attackers with valuable reconnaissance data about the system's file structure, user permissions, and potentially sensitive file locations. This information could be leveraged to plan more sophisticated attacks or to identify other vulnerabilities within the system. The risk is particularly concerning in environments where Firefox is used as a primary browser and where users may have access to sensitive data through local file systems. The vulnerability demonstrates how seemingly benign functionality like printing can become a security risk when proper access controls are not implemented throughout the entire application lifecycle. This type of attack pattern is consistent with the tactics described in the MITRE ATT&CK framework under the T1059.007 technique for command and scripting interpreter, where attackers exploit application vulnerabilities to gain access to system resources.
The mitigation strategy for CVE-2018-5107 primarily involves updating to Firefox version 58 or later, where the vulnerability has been patched. The fix implemented by Mozilla addresses the symbolic link validation logic within the printing subsystem to ensure that all file paths are properly validated before access is granted. Organizations should prioritize this update as a critical security measure, particularly in environments where Firefox is widely used and where sensitive data may be present on local systems. Additionally, system administrators should consider implementing additional monitoring for suspicious print job activities and review local file access controls to minimize potential impact. The vulnerability serves as a reminder of the importance of comprehensive security testing across all application components, including seemingly innocuous features like printing functionality, and highlights the need for robust input validation and access control mechanisms throughout the software development lifecycle.