CVE-2017-15298 in Git
Summary
by MITRE
Git through 2.14.2 mishandles layers of tree objects, which allows remote attackers to cause a denial of service (memory consumption) via a crafted repository, aka a Git bomb. This can also have an impact of disk consumption; however, an affected process typically would not survive its attempt to build the data structure in memory before writing to disk.
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Analysis
by VulDB Data Team • 01/03/2023
The vulnerability identified as CVE-2017-15298 represents a critical flaw in Git version 2.14.2 and earlier that exploits the handling of tree objects within repository structures. This issue manifests as a Git bomb attack pattern where maliciously crafted repositories can trigger excessive memory consumption during Git operations. The vulnerability stems from how Git processes nested tree objects, creating a scenario where the repository structure can exponentially expand the memory footprint required to parse and construct the internal data structures. This flaw specifically affects Git's internal tree traversal mechanisms and object database management systems, creating a path for attackers to craft repositories that appear normal but contain deeply nested tree references that cause memory allocation to spiral out of control.
The technical implementation of this vulnerability involves Git's object database processing where tree objects reference other tree objects recursively, creating a hierarchical structure that can be manipulated to cause excessive memory allocation. When Git attempts to parse a malicious repository, it follows the tree references without adequate depth or memory consumption limits, leading to a denial of service condition. The vulnerability operates at the core of Git's internal data structure management, specifically within the tree object parsing routines that are part of the standard Git workflow. Attackers can construct repositories with deeply nested tree objects that force Git to allocate increasingly larger amounts of memory during the parsing process, ultimately exhausting available system resources and causing the Git process to crash or become unresponsive.
The operational impact of this vulnerability extends beyond simple denial of service to include significant resource exhaustion that can affect entire systems hosting Git repositories. An attacker can craft a repository that consumes gigabytes of memory during Git operations, effectively rendering the system unusable for legitimate Git activities. The vulnerability is particularly dangerous because it can be triggered through normal Git operations such as cloning, fetching, or even simple repository browsing. The memory consumption typically occurs before any disk writes take place, meaning that the affected Git process cannot complete its operation and will terminate due to memory constraints. This makes the vulnerability particularly effective for disrupting Git-based development environments, CI/CD pipelines, and any system that relies on Git operations for code management and deployment workflows.
Mitigation strategies for CVE-2017-15298 primarily focus on upgrading to Git version 2.14.3 or later, where the vulnerability has been patched through improved tree object parsing and memory consumption limits. Organizations should implement repository scanning procedures to identify potentially malicious repositories before they are integrated into development environments. System administrators should consider implementing resource limits and monitoring for Git processes to detect unusual memory consumption patterns that might indicate an attack attempt. The vulnerability aligns with CWE-400 which addresses uncontrolled resource consumption, and can be categorized under ATT&CK technique T1499.002 which involves resource exhaustion attacks targeting data systems. Additionally, implementing proper repository access controls and validation procedures for code repositories can help prevent the introduction of malicious repositories into development environments. Organizations should also consider deploying Git-specific security tools that can analyze repository structures for potential Git bomb patterns and alert administrators to suspicious repository configurations.