CVE-2018-11243 in UPX
Summary
by MITRE
PackLinuxElf64::unpack in p_lx_elf.cpp in UPX 3.95 allows remote attackers to cause a denial of service (double free), limit the ability of a malware scanner to operate on the entire original data, or possibly have unspecified other impact via a crafted file.
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Analysis
by VulDB Data Team • 04/11/2025
The vulnerability identified as CVE-2018-11243 resides within the PackLinuxElf64::unpack function in the p_lx_elf.cpp source file of UPX version 3.95. This flaw represents a critical security issue that affects the unpacking process of Linux ELF executables within the UPX compression utility. The vulnerability manifests as a double free condition that occurs when processing specially crafted malicious files, fundamentally compromising the integrity of the decompression mechanism.
This vulnerability operates through a memory management error where the unpacking routine fails to properly handle memory allocation and deallocation sequences during the decompression of compressed ELF files. When an attacker provides a malformed input file, the function attempts to free the same memory block twice, creating a condition that can lead to arbitrary code execution or complete system crash. The double free vulnerability is classified under CWE-415, which specifically addresses the freeing of memory a second time, and can be exploited through various attack vectors including heap corruption and memory spraying techniques.
The operational impact of this vulnerability extends beyond simple denial of service conditions. Malware analysts and security scanners that rely on UPX for unpacking and analysis purposes face significant challenges when encountering files that trigger this flaw. The vulnerability can cause the scanner to fail completely, preventing proper analysis of potentially malicious content, thereby creating blind spots in security monitoring systems. This disruption affects the entire malware analysis workflow and can lead to false negatives where threats remain undetected due to the scanner's inability to process the complete file.
Furthermore, the vulnerability's potential for unspecified other impacts suggests that attackers may exploit the memory corruption to achieve more sophisticated outcomes beyond simple service disruption. The compromised memory state could enable attackers to manipulate the execution flow of the unpacking process, potentially allowing for code injection attacks or privilege escalation scenarios. This risk is particularly concerning in environments where UPX is used for automated malware analysis or security tooling that processes untrusted input files from multiple sources.
The remediation approach for CVE-2018-11243 requires immediate upgrading to UPX versions that have patched this memory management issue, specifically those released after the vulnerability disclosure. Organizations should implement comprehensive patch management procedures to ensure all instances of UPX are updated across their infrastructure. Additionally, security teams should consider implementing file validation mechanisms and sandboxing techniques to prevent exploitation of this vulnerability during the unpacking process. The ATT&CK framework categorizes this type of vulnerability under T1059.007 for execution through command and scripting interpreter, as attackers may leverage the memory corruption to execute malicious code within the unpacking environment. Organizations should also conduct regular vulnerability assessments to identify any other potentially affected components that might use similar memory management patterns, ensuring comprehensive protection against similar threats in their security infrastructure.