CVE-2016-10129 in libgit2
Summary
by MITRE
The Git Smart Protocol support in libgit2 before 0.24.6 and 0.25.x before 0.25.1 allows remote attackers to cause a denial of service (NULL pointer dereference) via an empty packet line.
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Analysis
by VulDB Data Team • 11/15/2022
The vulnerability identified as CVE-2016-10129 represents a critical denial of service flaw within the libgit2 library's implementation of the Git Smart Protocol. This issue affects versions prior to 0.24.6 and 0.25.x before 0.25.1, making it a widespread concern for systems utilizing this popular Git library implementation. The Git Smart Protocol is a core component of Git's communication mechanism that enables efficient data transfer between Git repositories, particularly when cloning, fetching, or pushing operations occur over network connections. The vulnerability manifests when the library encounters an empty packet line during Smart Protocol communication, which triggers an unexpected NULL pointer dereference condition that ultimately leads to process termination.
The technical root cause of this vulnerability lies in inadequate input validation within libgit2's packet parsing logic. When processing Git Smart Protocol messages, the library fails to properly handle cases where packet lines contain no data or are entirely empty. This omission creates a scenario where the application attempts to dereference a NULL pointer when processing such malformed packets, resulting in an immediate crash of the target process. The flaw specifically impacts the protocol handler's ability to gracefully manage edge cases in packet transmission, where empty packet lines may be sent as part of normal Git communication patterns or as malicious payloads. This type of vulnerability falls under the CWE-476 category of NULL Pointer Dereference, which is classified as a fundamental programming error that can lead to system instability and denial of service conditions. The vulnerability demonstrates poor error handling practices in network protocol implementations and highlights the importance of robust input validation in security-critical software components.
The operational impact of CVE-2016-10129 extends beyond simple service disruption, as it can be exploited by remote attackers to systematically destabilize Git services and applications that depend on libgit2. Attackers can craft malicious Git protocol packets containing empty lines and transmit them to vulnerable systems, causing immediate process termination and service unavailability. This vulnerability particularly affects Git servers, continuous integration systems, and any application that relies on libgit2 for Git operations, potentially leading to widespread service degradation across development environments. The exploitability of this vulnerability is relatively straightforward, requiring only the ability to send specially crafted Git protocol messages to the target system. The impact is particularly severe in automated environments where Git operations are frequent and critical to application functionality, as a single malicious packet can cause cascading failures in dependent systems. This vulnerability also aligns with ATT&CK technique T1499.004, which involves network denial of service attacks targeting communication protocols and services.
Mitigation strategies for CVE-2016-10129 require immediate patching of affected libgit2 installations to versions 0.24.6 or 0.25.1 and later, which contain the necessary fixes for proper packet line handling. System administrators should prioritize updating all affected systems, particularly those running Git servers or applications that process untrusted Git protocol data. Additionally, implementing network-level protections such as firewall rules that restrict Git protocol access to trusted sources can provide temporary defense while patches are deployed. Organizations should also consider implementing monitoring and alerting for unusual Git protocol traffic patterns that might indicate exploitation attempts. The fix implemented in patched versions addresses the NULL pointer dereference by adding proper validation checks for empty packet lines and ensuring graceful handling of malformed protocol data. Security teams should conduct comprehensive vulnerability assessments to identify all systems using affected libgit2 versions and establish incident response procedures for potential exploitation attempts. This vulnerability underscores the importance of maintaining up-to-date software libraries and implementing proper input validation in network protocol implementations to prevent similar issues from occurring in the future.