CVE-2025-53817 is a medium-severity vulnerability identified in the ipavlov variant of the 7-Zip file archiver, specifically affecting versions prior to 25.0.0. The issue stems from a NULL pointer dereference in the Compound Document handler component of 7-Zip. Compound Documents are a file format used to store multiple streams of data within a single file, commonly encountered in Microsoft Office documents and other complex file types. When 7-Zip attempts to extract or process a crafted Compound Document, it may dereference a NULL pointer, causing the application to crash or terminate unexpectedly. This results in a denial of service (DoS) condition, where the affected software becomes unavailable or unresponsive. The vulnerability does not require any authentication or user interaction, and the attack vector is local (AV:L), meaning an attacker must have the ability to supply or open a malicious archive on the target system. The CVSS 4.0 base score of 5.5 reflects the moderate impact, with no confidentiality, integrity, or availability impact beyond the local DoS. The vulnerability was fixed in version 25.0.0 of 7-Zip, which includes a patch to properly handle NULL pointers in the Compound Document extraction logic. There are currently no known exploits in the wild targeting this vulnerability, but the presence of a fix indicates the potential for exploitation if unpatched systems process malicious archives.

For European organizations, the primary impact of CVE-2025-53817 is the potential disruption of services or workflows that rely on 7-Zip for archive extraction, particularly when handling Compound Document formats. This could affect IT operations, automated processing pipelines, or end-user activities involving compressed files. While the vulnerability does not lead to data leakage or privilege escalation, denial of service conditions can cause productivity loss and may interrupt critical business processes. Organizations in sectors with high document exchange volumes, such as legal, finance, and government, could experience operational delays if attackers supply malicious archives to trigger crashes. Additionally, if 7-Zip is integrated into backend systems or automated tools, the DoS could propagate to larger system outages. The local attack vector limits remote exploitation, but social engineering or insider threats could still leverage this vulnerability by convincing users to open malicious archives. Given 7-Zip's widespread use as a free and open-source archiver across Europe, unpatched systems remain at risk of service interruptions.

European organizations should prioritize upgrading all instances of 7-Zip to version 25.0.0 or later, where the NULL pointer dereference issue is resolved. Beyond patching, organizations should implement strict file handling policies that include scanning all incoming archives with updated antivirus and endpoint detection tools to detect malformed or suspicious Compound Documents. Restricting the use of 7-Zip to trusted users and limiting the acceptance of archives from unverified sources can reduce exposure. For automated systems, incorporate input validation and error handling to gracefully manage unexpected archive content without crashing. Monitoring application logs for unexpected 7-Zip crashes can help detect attempted exploitation. Additionally, educating users about the risks of opening untrusted archives and enforcing least privilege principles for file extraction operations will further mitigate risk. Finally, consider sandboxing archive extraction processes to contain potential crashes and prevent wider system impact.