CVE-2016-8569 in libgit2
Summary
by MITRE
The git_oid_nfmt function in commit.c in libgit2 before 0.24.3 allows remote attackers to cause a denial of service (NULL pointer dereference) via a cat-file command with a crafted object file.
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Analysis
by VulDB Data Team • 11/11/2022
The vulnerability identified as CVE-2016-8569 represents a critical denial of service flaw within the libgit2 library version 0.24.2 and earlier. This issue specifically affects the git_oid_nfmt function located in the commit.c file, which serves as a core component in handling object identifiers within the git version control system. The vulnerability arises from inadequate input validation when processing crafted object files through the cat-file command, creating a scenario where remote attackers can trigger a NULL pointer dereference condition that ultimately results in application termination.
The technical implementation of this vulnerability stems from the improper handling of object identifiers during the formatting process. When the git_oid_nfmt function processes a malformed or specially crafted object file, it fails to properly validate the input data structure before attempting to dereference pointers within the object's memory layout. This flaw directly maps to CWE-476 which describes NULL pointer dereference conditions, where an application attempts to access memory through a null reference. The vulnerability is particularly concerning because it can be exploited remotely through the cat-file command, which is a standard git utility for examining object files, making it accessible to attackers without requiring local system access.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged to create persistent denial of service conditions in systems relying on libgit2 for git operations. Attackers can craft malicious object files that, when processed by applications using vulnerable versions of libgit2, will cause the target application to crash and terminate unexpectedly. This affects a wide range of applications including git servers, continuous integration systems, and any software that integrates libgit2 for version control operations. The vulnerability demonstrates a classic remote code execution pathway through resource exhaustion and service interruption, which aligns with ATT&CK technique T1499.1 for network denial of service attacks.
Mitigation strategies for CVE-2016-8569 primarily focus on immediate version updates to libgit2 0.24.3 or later, which contain the necessary patches to address the NULL pointer dereference issue. Organizations should also implement input validation measures and sanitize all object files before processing them through git operations. Additionally, network segmentation and access controls can help limit the potential impact of exploitation attempts. The fix implemented in version 0.24.3 involves strengthening the input validation within the git_oid_nfmt function to properly handle malformed object identifiers and prevent the NULL pointer dereference condition that previously occurred during object file processing.