CVE-2025-11579 is a vulnerability identified in the rardecode library maintained by nwaples, specifically affecting versions up to 2.1.1. The root cause is the failure to impose restrictions on the dictionary size parameter when parsing RAR archives. The dictionary size in RAR compression dictates the amount of memory allocated for decompression buffers. An attacker can craft a RAR file with an excessively large dictionary size value, causing the rardecode library to allocate an unbounded amount of memory. This leads to an out-of-memory condition, crashing the application or service utilizing the library, resulting in a denial of service (DoS). The vulnerability does not require any privileges or user interaction, making it remotely exploitable by simply processing the malicious archive. The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L) indicates network attack vector, low complexity, no privileges or user interaction needed, unchanged scope, and impact limited to availability. No known exploits have been reported in the wild yet, but the vulnerability poses a risk to any software or service that uses rardecode for RAR file decompression. The lack of patch links suggests a fix may not yet be publicly available, so mitigation currently relies on defensive controls and monitoring. This vulnerability is categorized under CWE-789 (Memory Allocation with Excessive Size Value), a common class of resource exhaustion issues.

For European organizations, the primary impact is denial of service due to application or service crashes when processing malicious RAR files. This can disrupt business operations, especially in sectors that handle large volumes of compressed data such as media, software development, and IT services. Systems that automatically scan or decompress RAR archives (e.g., antivirus, file storage, or content management systems) are particularly at risk. While confidentiality and integrity are not directly affected, availability degradation can lead to operational downtime and potential cascading effects in critical infrastructure or service delivery. The medium CVSS score reflects moderate risk, but the ease of exploitation and lack of required privileges increase the threat level. Organizations relying on third-party software embedding rardecode should assess their exposure. Additionally, denial of service attacks could be leveraged as part of broader attack campaigns targeting European entities, especially those with high dependency on file decompression services.

1. Monitor for updates from the rardecode project and apply patches promptly once available. 2. Until a patch is released, implement input validation to reject RAR files with unusually large dictionary size fields. 3. Deploy resource limits on memory allocation for decompression processes to prevent excessive consumption. 4. Use sandboxing or isolated environments for processing untrusted RAR files to contain potential crashes. 5. Employ network-level controls to detect and block suspicious RAR files or traffic patterns indicative of exploitation attempts. 6. Review and update incident response plans to handle potential denial of service incidents related to this vulnerability. 7. Engage with software vendors that incorporate rardecode to confirm their mitigation status and timelines. 8. Consider alternative decompression libraries with better input validation if immediate patching is not feasible.