CVE-2017-11124 in xar
Summary
by MITRE
libxar.so in xar 1.6.1 has a NULL pointer dereference in the xar_unserialize function in archive.c.
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Analysis
by VulDB Data Team • 12/12/2022
The vulnerability identified as CVE-2017-11124 resides within the libxar.so library component of the xar archive utility version 1.6.1. This issue manifests as a NULL pointer dereference occurring within the xar_unserialize function located in the archive.c source file. The xar utility is commonly used for creating and extracting archive files, particularly in macOS environments where it serves as the native archive format for various system components and applications. The flaw represents a critical reliability issue that can potentially lead to application crashes or system instability when processing malformed archive files.
The technical nature of this vulnerability stems from improper input validation within the serialization and deserialization processes of xar archive files. When the xar_unserialize function attempts to parse and reconstruct archive data structures, it fails to adequately check for NULL pointer conditions before dereferencing pointers that may not have been properly initialized. This particular flaw falls under the category of improper input validation and memory management issues that are commonly classified as CWE-476. The vulnerability specifically affects the handling of archive metadata and file structure information during the deserialization phase, where the library assumes certain data pointers will contain valid references without proper null checking mechanisms.
The operational impact of this vulnerability extends beyond simple application crashes to potentially enable more sophisticated attack vectors. When exploited, the NULL pointer dereference can cause the xar utility to terminate abruptly, leading to denial of service conditions for applications that rely on this library for archive processing. In environments where xar archives are frequently processed, such as software deployment systems, backup utilities, or system recovery tools, this vulnerability could be leveraged to disrupt normal operations. The issue is particularly concerning in automated environments where archive processing occurs without user intervention, as it could lead to cascading failures in system operations.
Security practitioners should consider this vulnerability in the context of broader attack surface analysis and incident response planning. The flaw demonstrates the importance of proper error handling and input validation in system libraries, particularly those handling user-supplied data. Organizations should prioritize updating to patched versions of the xar utility and monitoring for exploitation attempts in their environments. The vulnerability aligns with ATT&CK technique T1499.001 which covers network denial of service attacks, and represents a classic example of how memory corruption vulnerabilities can be exploited to achieve system instability. Mitigation strategies should include immediate patching of affected systems, implementation of proper input validation in custom applications that interface with xar libraries, and monitoring for abnormal process termination patterns. Additionally, defensive measures such as sandboxing archive processing operations and implementing proper error handling in applications that utilize libxar.so can help reduce the potential impact of this and similar vulnerabilities.