CVE-2018-17093 in xar
Summary
by MITRE
An issue has been discovered in mackyle xar 1.6.1. There is a NULL pointer dereference in xar_get_path in lib/util.c.
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Analysis
by VulDB Data Team • 05/16/2023
The vulnerability identified as CVE-2018-17093 resides within the mackyle xar 1.6.1 library, specifically within the xar_get_path function located in lib/util.c. This issue represents a critical NULL pointer dereference that can lead to application crashes and potentially more severe security implications. The flaw occurs when the library processes certain archive files, particularly those with malformed or unexpected path structures that cause the function to attempt dereferencing a null pointer. Such vulnerabilities are particularly dangerous in archive processing libraries since they can be exploited through crafted input files that trigger the vulnerable code path during normal archive extraction or parsing operations.
The technical nature of this vulnerability aligns with CWE-476 which defines NULL Pointer Dereference as a condition where a null value is dereferenced, leading to a crash or potential exploitation. The vulnerability manifests when the xar_get_path function fails to properly validate input parameters or handle edge cases in path processing, resulting in a scenario where a pointer expected to contain valid data becomes NULL and is subsequently dereferenced. This type of flaw commonly occurs in C-based libraries where memory management and input validation are not adequately implemented, particularly in functions that parse complex data structures like archive file formats. The flaw demonstrates poor defensive programming practices and highlights the importance of proper null checking in systems processing external data.
The operational impact of this vulnerability extends beyond simple application crashes, as it can be leveraged in denial-of-service attacks against systems that utilize the xar library for archive processing. When exploited, this vulnerability can cause applications using the library to terminate unexpectedly, potentially leading to service disruption for legitimate users. Systems that process untrusted archive files, such as email servers, file transfer systems, or content delivery networks, become particularly vulnerable to this type of attack. The vulnerability is especially concerning in automated processing environments where multiple archives are processed sequentially, as a single malicious archive could cause cascading failures throughout the system. From an attack perspective, this vulnerability maps to ATT&CK technique T1203 which involves gaining access to systems through manipulation of file processing functions, and T1499 which covers network disruption through service availability attacks.
Mitigation strategies for CVE-2018-17093 should prioritize immediate patching of the affected library to version 1.6.2 or later, which contains the necessary fixes for the NULL pointer dereference issue. Organizations should implement comprehensive input validation for all archive files processed through the xar library, including signature verification and format checking before any processing occurs. Additionally, deploying sandboxing mechanisms for archive processing can help contain potential exploitation attempts and prevent system-wide failures. System administrators should monitor for any unusual application crashes or service disruptions that might indicate exploitation attempts, while also implementing proper logging and alerting for archive processing activities. The fix typically involves adding proper null pointer checks before dereferencing any pointers returned from path parsing functions, ensuring that all input validation occurs before any processing begins. Security teams should also consider implementing network segmentation and access controls to limit the potential impact of successful exploitation attempts, particularly in environments where the vulnerable library is used extensively for processing external content.