CVE-2018-5650 in Long Range Zip
Summary
by MITRE
In Long Range Zip (aka lrzip) 0.631, there is an infinite loop and application hang in the unzip_match function in runzip.c. Remote attackers could leverage this vulnerability to cause a denial of service via a crafted lrz file.
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Analysis
by VulDB Data Team • 01/20/2023
The vulnerability identified as CVE-2018-5650 affects Long Range Zip (lrzip) version 0.631, a compression utility designed for handling large files with high compression ratios. This flaw manifests as an infinite loop within the unzip_match function located in the runzip.c source file, creating a critical denial of service condition that can be remotely exploited by attackers. The vulnerability specifically targets the decompression process when handling maliciously crafted lrz files, where the flawed algorithm fails to properly terminate loop iterations during pattern matching operations.
The technical root cause of this vulnerability lies in improper boundary checking and loop termination logic within the unzip_match function. When the decompression routine encounters specific malformed data patterns in the compressed file, the matching algorithm enters an infinite loop where it continuously iterates without making progress toward decompressing the data. This condition occurs because the function fails to validate loop counters or pattern matching parameters against expected bounds, allowing an attacker to craft input data that causes the decompression engine to hang indefinitely. The flaw represents a classic example of insufficient input validation and inadequate loop control mechanisms that can be exploited through carefully constructed malicious inputs.
The operational impact of this vulnerability extends beyond simple resource exhaustion, as it can be leveraged by remote attackers to cause sustained denial of service against systems running lrzip. When exploited, the infinite loop consumes system resources including cpu cycles and memory, potentially leading to system instability or complete service unavailability. This vulnerability affects any system that processes lrz files through lrzip, including automated backup systems, file sharing platforms, and any application that relies on lrzip for decompression operations. The remote exploitation capability means attackers do not need local access to trigger the vulnerability, making it particularly dangerous in networked environments where lrzip is used to process user-uploaded content.
Mitigation strategies for CVE-2018-5650 should prioritize immediate patching of lrzip installations to version 0.632 or later, which contains the necessary fixes for the infinite loop condition. Organizations should implement input validation measures to sanitize lrz files before processing, including size limits and format verification checks. Network segmentation and access controls can help reduce exposure by limiting direct access to lrzip processing endpoints. The vulnerability aligns with CWE-835, which catalogs issues related to infinite loops and improper loop termination, and represents a potential entry point for attackers following ATT&CK technique T1499.002, which involves network denial of service attacks. System administrators should also consider implementing monitoring and alerting mechanisms to detect unusual cpu utilization patterns that may indicate exploitation attempts, while maintaining regular security updates to protect against similar vulnerabilities in compression utilities.