CVE-2008-2942 in Mercurial
Summary
by MITRE
Directory traversal vulnerability in patch.py in Mercurial 1.0.1 allows user-assisted attackers to modify arbitrary files via ".." (dot dot) sequences in a patch file.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 08/14/2019
The vulnerability identified as CVE-2008-2942 represents a critical directory traversal flaw within the Mercurial distributed version control system version 1.0.1. This security weakness resides in the patch.py script responsible for processing patch files within the Mercurial ecosystem, creating a potential attack vector that could allow malicious actors to manipulate files outside of intended directories. The vulnerability specifically manifests when the system processes patch files containing ".." sequences, which are standard directory navigation elements used to reference parent directories in file systems.
The technical implementation of this flaw stems from inadequate input validation within the patch processing functionality of Mercurial. When a user-supplied patch file contains directory traversal sequences such as "../" or "..\", the patch.py script fails to properly sanitize these path references before executing file operations. This failure creates a condition where an attacker can craft malicious patch files that, when applied to a repository, would cause the system to write or modify files in arbitrary locations on the target file system. The vulnerability operates at the file system level, bypassing normal access controls and potentially allowing unauthorized modifications to system files, configuration data, or other sensitive resources.
The operational impact of CVE-2008-2942 extends beyond simple file corruption, as it provides attackers with the capability to escalate privileges and potentially execute arbitrary code on affected systems. An attacker could exploit this vulnerability by creating a malicious patch file that targets critical system files, configuration directories, or even binary executables within the Mercurial repository environment. This vulnerability is particularly dangerous in collaborative development environments where patch files are frequently shared and applied, as it could enable an attacker to compromise the integrity of the entire version control system. The attack requires user assistance, meaning a legitimate user must willingly apply the malicious patch, but this requirement does not significantly reduce the overall risk given that patch application is a routine operation in version control workflows.
Security professionals should recognize this vulnerability as a classic example of CWE-22 - Improper Limitation of a Pathname to a Restricted Directory, which is categorized under the broader weakness of path traversal attacks. The vulnerability aligns with ATT&CK technique T1059.007 - Command and Scripting Interpreter: Python, as it involves exploitation of Python-based scripts within a version control system. Organizations using Mercurial 1.0.1 should immediately implement mitigations including patch file validation, mandatory code review processes for all patch files, and restricted permissions for patch application operations. The most effective remediation involves upgrading to a patched version of Mercurial where proper input sanitization has been implemented to prevent directory traversal sequences from being processed as legitimate file paths. Additionally, system administrators should consider implementing automated scanning tools to detect potentially malicious patch files and establish monitoring protocols to identify unauthorized file modifications in version control environments.