CVE-2015-0838 in Dulwich
Summary
by MITRE
Buffer overflow in the C implementation of the apply_delta function in _pack.c in Dulwich before 0.9.9 allows remote attackers to execute arbitrary code via a crafted pack file.
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Analysis
by VulDB Data Team • 05/02/2022
The vulnerability identified as CVE-2015-0838 represents a critical buffer overflow flaw within the Dulwich library's implementation of git pack file processing. This issue affects versions of Dulwich prior to 0.9.9 and specifically targets the apply_delta function located in the _pack.c source file. The flaw arises during the handling of git pack files, which are binary formats used by git to efficiently store and transfer repository data. When a maliciously crafted pack file is processed by the vulnerable library, the buffer overflow condition can be triggered, potentially allowing remote attackers to execute arbitrary code on systems running affected versions.
The technical implementation of this vulnerability stems from insufficient input validation and boundary checking within the apply_delta function. This function is responsible for applying delta compression to git objects during pack file processing, where it calculates and applies differences between object versions to reduce storage requirements. The buffer overflow occurs when the function fails to properly validate the size of data being read from the pack file, allowing an attacker to provide input that exceeds the allocated buffer space. This condition creates a classic stack-based buffer overflow scenario that can be exploited to overwrite adjacent memory locations, potentially leading to code execution control flow redirection.
From an operational impact perspective, this vulnerability poses significant risks to systems that rely on Dulwich for git repository operations, particularly those that process untrusted pack files from remote sources. Attackers could craft malicious pack files that, when processed by vulnerable applications, would enable remote code execution with the privileges of the affected process. The attack vector is particularly concerning because it can be executed remotely without requiring authentication, making it a high-severity threat for any system that handles git operations from untrusted sources. This vulnerability affects not only direct applications using Dulwich but also any software that depends on it for git functionality, potentially creating widespread impact across development environments and continuous integration systems.
The vulnerability maps directly to CWE-121, which describes stack-based buffer overflow conditions, and aligns with ATT&CK technique T1059.007 for execution through scripting. Organizations should prioritize immediate patching of all systems running affected versions of Dulwich to mitigate this risk. The recommended mitigation strategy includes updating to Dulwich version 0.9.9 or later, implementing strict input validation for pack file processing, and establishing network segmentation to limit exposure to untrusted git content. Additionally, security monitoring should be enhanced to detect unusual git pack file processing activities that might indicate exploitation attempts. Organizations should also consider implementing sandboxing techniques for git operations involving external repositories and maintaining up-to-date threat intelligence regarding similar vulnerabilities in version control systems.