CVE-2026-48109
HighCVSS 8.2Exploitation Probability (EPSS)
Low risk21th percentile - higher than 21% of all known CVEs
Summary
The MessagePack library for C# has a vulnerability in the optional LZ4 decompression path that can lead to out-of-bounds reads. An attacker can send a crafted MessagePack payload, potentially causing process termination.
Risk Assessment
This vulnerability may lead to denial of service and potential memory disclosure. Organizations should be aware of the risks associated with using outdated versions of the library.
Recommendation
It is recommended to upgrade to version 2.5.301 or 3.1.7 to mitigate this vulnerability and secure the system against potential attacks.
Original NVD description (English source)
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, A vulnerability exists in the optional LZ4 decompression path used by MessagePack compression modes Lz4Block and Lz4BlockArray. The decoder implementation is based on a deprecated fast-decompression algorithm that does not take a source-length bound. A remote attacker can send a crafted MessagePack payload with manipulated LZ4 token/length fields to force out-of-bounds reads from the compressed input buffer. In affected environments, this can trigger an AccessViolationException during decompression, causing process termination (denial of service). Under some conditions, limited unintended memory disclosure from over-read data may also be possible before failure. This vulnerability is fixed in 2.5.301 and 3.1.7.