CVE-2025-11579 is a vulnerability identified in the nwaples rardecode library, versions up to and including 2.1.1. The issue stems from improper handling of the dictionary size parameter when parsing RAR archive files. Specifically, the library fails to impose limits on the dictionary size, which can be manipulated by an attacker through a crafted RAR file to request an excessively large memory allocation. This leads to an out-of-memory condition, causing the application using the library to crash, resulting in a denial of service (DoS). The vulnerability is classified under CWE-789 (Memory Allocation with Excessive Size Value). The CVSS v3.1 base score is 5.3 (medium severity), with the vector indicating that the attack can be performed remotely (AV:N), requires low attack complexity (AC:L), no privileges (PR:N), no user interaction (UI:N), and impacts availability only (A:L) without affecting confidentiality or integrity. No patches or fixes are currently linked, and no known exploits have been reported in the wild. The vulnerability affects software that integrates rardecode for RAR file decompression, which is common in various open-source and proprietary applications. The flaw can be exploited by an attacker simply by providing a malicious RAR file to the vulnerable system, potentially causing service interruptions or crashes in applications that process such archives.

For European organizations, the primary impact of CVE-2025-11579 is on the availability of systems that utilize the vulnerable rardecode library for RAR file decompression. This could affect file extraction services, backup solutions, antivirus scanners, or any software that processes RAR archives. A successful exploit would cause an out-of-memory crash, leading to denial of service, which can disrupt business operations, especially in environments where automated processing of compressed files is critical. While the vulnerability does not compromise data confidentiality or integrity, the resulting downtime may affect service level agreements and operational continuity. Organizations in sectors such as finance, manufacturing, and IT services that rely heavily on file archiving and transfer may experience operational delays or interruptions. Additionally, the lack of authentication and user interaction requirements means that exposure is broad, increasing the risk of opportunistic attacks. Given the medium severity, the impact is significant but not catastrophic, provided mitigation steps are implemented promptly.

1. Monitor for updates from the nwaples rardecode project and apply patches promptly once available to address the dictionary size restriction flaw. 2. Until patches are released, implement input validation to reject RAR files with unusually large dictionary sizes or suspicious metadata before processing. 3. Employ resource limits and memory usage caps on processes handling RAR decompression to prevent out-of-memory conditions from crashing critical services. 4. Use sandboxing or isolated environments for decompressing untrusted RAR files to contain potential crashes and prevent wider system impact. 5. Review and update antivirus and intrusion detection systems to flag and block malformed RAR files that could exploit this vulnerability. 6. Educate users and administrators about the risks of processing untrusted archives and encourage cautious handling of RAR files from unknown sources. 7. Conduct regular audits of software dependencies to identify and track usage of vulnerable rardecode versions within organizational systems. 8. Consider alternative decompression libraries with better input validation if immediate patching is not feasible.