CVE-2025-53816: 
7-Zip vulnerability analysis and mitigation

7-Zip, a popular file archiver with high compression capabilities, was found to contain a critical memory corruption vulnerability (CVE-2025-53816) affecting all versions prior to 25.0.0. The vulnerability was discovered by Jaroslav Lobačevski from GitHub Security Lab and was assigned a CVSS score of 5.5 (Medium severity). The issue was identified on April 24, 2025, acknowledged on April 29, and subsequently fixed in version 25.0.0 released on July 5, 2025 (GitHub Security Lab, Cybersecurity News).

The vulnerability is a heap-based buffer overflow (CWE-122) in the RAR5 decoder implementation, specifically in the NCompress::NRar5::CDecoder component. The flaw occurs when the software attempts to recover from corrupted archive data by filling damaged sections with zeros. The root cause is a miscalculation of the rem value during memory zeroing operations, where MyZeroMemory(window + winPos, (sizet)rem) is called with an incorrectly calculated rem parameter. The lzEnd variable, which influences the calculation, depends on the size of previous items in the archive and can be controlled by attackers ([GitHub Security Lab](https://securitylab.github.com/advisories/GHSL-2025-0587-Zip/)).

While the vulnerability is unlikely to lead to arbitrary code execution, it poses significant risks for denial-of-service attacks. The flaw allows attackers to write zeros beyond the allocated heap buffer, potentially corrupting adjacent memory regions and causing application crashes. Testing demonstrated that specially crafted RAR5 files could trigger heap buffer overflows, with one proof-of-concept causing a write of 9,469 bytes beyond the allocated buffer (GitHub Security Lab, Cybersecurity News).

The vulnerability has been fixed in 7-Zip version 25.0.0. Users and organizations are strongly recommended to upgrade to this version or later. Since 7-Zip lacks automatic update functionality, users must manually download and install the latest version from the official website. Organizations processing untrusted archive files should implement additional security measures, including restricting access to potentially malicious RAR5 archives and deploying comprehensive file validation before processing (Cybersecurity News).