CVE-2026-48514

Name of the Vulnerable Software and Affected Versions MessagePack for C# versions prior to 2.5.301 MessagePack for C# versions prior to 3.1.7

Description The UnsafeBlitFormatterBase<T>.Deserialize() function reads an attacker-controlled byteLength from an extension payload and allocates an array based on that value before validating it against the extension header length or remaining payload bytes. While the outer extension header is bounded by available input, this bound is not used to constrain the inner byteLength before allocation, allowing a small payload to request a very large T[] allocation.

Recommendations Update to version 2.5.301. Update to version 3.1.7.