CVE-2014-9706 in Dulwich
Summary
by MITRE
The build_index_from_tree function in index.py in Dulwich before 0.9.9 allows remote attackers to execute arbitrary code via a commit with a directory path starting with .git/, which is not properly handled when checking out a working tree.
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Analysis
by VulDB Data Team • 05/02/2022
The vulnerability identified as CVE-2014-9706 resides within the Dulwich library, a pure python implementation of the git distributed version control system. This flaw affects versions prior to 099 and specifically targets the build_index_from_tree function located in the index.py file. The vulnerability represents a critical security issue that enables remote code execution through a carefully crafted commit that contains a directory path beginning with .git/. This particular path structure creates a dangerous condition when the system attempts to check out a working tree, as it fails to properly sanitize or validate such directory references.
The technical mechanism behind this vulnerability stems from inadequate input validation within the git repository indexing process. When Dulwich processes a commit containing a directory path that starts with .git/, the system does not properly handle this special case during the checkout operation. This failure creates a path traversal condition where attacker-controlled data can influence the file system operations performed by the library. The vulnerability essentially allows an attacker to manipulate the working tree checkout process to write files to locations outside of the intended repository structure, potentially leading to arbitrary code execution on systems running vulnerable versions of Dulwich.
From an operational impact perspective, this vulnerability poses significant risks to any system or application that relies on Dulwich for git operations and is exposed to untrusted commit data. The remote exploitation capability means that attackers can craft malicious commits and push them to repositories that are subsequently processed by vulnerable systems. This could occur in various scenarios including continuous integration systems, git hosting platforms, or any application that automatically processes incoming commits through Dulwich. The potential for arbitrary code execution makes this vulnerability particularly dangerous as it could allow attackers to gain full control over affected systems or compromise the integrity of the entire git repository infrastructure.
The vulnerability aligns with CWE-22 Path Traversal and CWE-78 Command Injection categories, representing a classic path traversal attack that leverages git's file system operations. It also maps to ATT&CK technique T1059.001 Command and Scripting Interpreter: PowerShell and T1059.007 Command and Scripting Interpreter: Python, as the exploitation involves manipulating python-based git operations. Organizations using Dulwich in production environments should immediately upgrade to version 0.9.9 or later to mitigate this risk. Additionally, administrators should implement proper input validation for git operations, monitor for suspicious commit patterns, and consider implementing network segmentation to limit the potential impact of such attacks. The fix implemented in version 0.9.9 addresses the core validation issue by properly sanitizing directory paths during the checkout process, ensuring that .git/ prefixed paths are handled appropriately without allowing unauthorized file system access.