CVE-2017-11189 in unrar-free
Summary
by MITRE
unrarlib.c in unrar-free 0.0.1 might allow remote attackers to cause a denial of service (NULL pointer dereference and application crash), which could be relevant if unrarlib is used as library code for a long-running application.
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Analysis
by VulDB Data Team • 10/25/2019
The vulnerability identified as CVE-2017-11189 resides within the unrar-free 0.0.1 library implementation, specifically in the unrarlib.c file where a NULL pointer dereference condition can be exploited by remote attackers. This flaw represents a critical security concern for systems that rely on unrar-free as a library component for processing archive files. The vulnerability manifests when the library encounters malformed or specially crafted rar archive files that trigger unexpected behavior during decompression operations. The NULL pointer dereference occurs during the processing of archive metadata or file structures that the library fails to properly validate or handle, leading to application termination and potential system instability.
The technical exploitation of this vulnerability involves sending maliciously constructed rar archive files to applications that utilize the unrar-free library for decompression tasks. When the library attempts to process these malformed archives, it encounters a scenario where a pointer expected to reference valid memory structures becomes NULL, causing the application to crash upon dereferencing this invalid pointer. This type of flaw falls under CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations. The vulnerability is particularly concerning for long-running applications that continuously process user-uploaded content or network streams, as a successful exploit can lead to persistent denial of service conditions that degrade system availability.
The operational impact of CVE-2017-11189 extends beyond simple application crashes to potentially compromise system reliability and availability in production environments. Systems that depend on unrar-free for automated archive processing, such as file upload handlers, email filtering systems, or content management platforms, become vulnerable to targeted attacks that can cause service disruption. The vulnerability's relevance for long-running applications means that even a single successful exploitation can result in extended downtime or require system restarts to restore normal operations. From an attacker perspective, this represents a low-effort, high-impact vector that can be leveraged through the ATT&CK technique of "Application Layer Protocol" to exploit processing functions within legitimate software stacks.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected unrar-free library versions to address the NULL pointer dereference condition. Organizations should implement input validation and sanitization measures for all archive processing operations to prevent malformed files from reaching the unrar-free library components. Additionally, deploying intrusion detection systems that can identify and block suspicious archive file patterns can provide defense-in-depth protection. The implementation of application sandboxing or containerization for archive processing functions helps limit the impact of potential exploitation attempts. Security monitoring should include detection of application crashes or restarts that may indicate successful exploitation attempts, while regular security assessments of third-party library dependencies can help identify similar vulnerabilities in other software components.