CVE-2023-23456 in UPX
Summary
by MITRE • 01/12/2023
A heap-based buffer overflow issue was discovered in UPX in PackTmt::pack() in p_tmt.cpp file. The flow allows an attacker to cause a denial of service (abort) via a crafted file.
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Analysis
by VulDB Data Team • 10/07/2025
The heap-based buffer overflow vulnerability identified as CVE-2023-23456 resides within the UPX (Ultimate Packer for eXecutables) compression utility, specifically within the PackTmt::pack() function located in the p_tmt.cpp source file. This flaw represents a critical security weakness that can be exploited through the manipulation of input data during the packing process, potentially leading to system instability and denial of service conditions. The vulnerability manifests when the application processes specially crafted executable files that trigger improper memory handling within the compression algorithm, creating a scenario where heap memory is overwritten beyond its allocated boundaries.
The technical implementation of this vulnerability stems from inadequate bounds checking and memory management within the PackTmt::pack() function, which operates as part of UPX's compression routines for executable files. When an attacker supplies a maliciously constructed input file, the function fails to properly validate the size or structure of incoming data before attempting to copy or process it into heap-allocated buffers. This deficiency creates an exploitable condition where the program attempts to write data beyond the allocated memory space, causing memory corruption that can result in program termination or unpredictable behavior. The vulnerability is classified as a heap-based buffer overflow, which falls under the CWE-122 category of insufficient checking of heap buffer bounds, making it particularly dangerous as it can lead to arbitrary code execution or system crashes.
The operational impact of CVE-2023-23456 extends beyond simple denial of service, as it represents a potential vector for more sophisticated attacks within environments where UPX is used for executable compression or distribution. Attackers can leverage this vulnerability to cause applications that utilize UPX-packed executables to crash, effectively disrupting service availability and potentially creating opportunities for further exploitation. The vulnerability affects systems that process or execute UPX-compressed files, including software distribution platforms, security scanning tools, and any environment where executable files undergo compression before deployment. This weakness is particularly concerning in enterprise environments where UPX is commonly used for code optimization and distribution, as it could be exploited to disrupt critical infrastructure operations or serve as a stepping stone for more advanced attacks.
Mitigation strategies for CVE-2023-23456 should prioritize immediate patching of affected UPX versions to address the heap buffer overflow condition. Organizations should implement strict input validation procedures for any files processed through UPX compression utilities, including the deployment of sandboxing mechanisms to isolate potentially malicious inputs. Network security controls should be enhanced to monitor for suspicious UPX file processing activities and implement automated scanning for vulnerable versions of the utility. The ATT&CK framework categorizes this vulnerability under T1059.007 for execution through compressed files and T1497.001 for defense evasion through file manipulation, highlighting the need for comprehensive security monitoring. Additionally, system administrators should consider implementing application whitelisting policies that restrict execution of UPX binaries to trusted sources and establish regular vulnerability assessments to identify other potential heap-based buffer overflow conditions within similar compression utilities and binary processing frameworks.