CVE-2026-48517: medium-severity vulnerability in MessagePack-CSharp
MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments
Published · Updated
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13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.3epss 0.3%
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePack-CSharp's typeless deserialization includes MessagePackSerializerOptions.ThrowIfDeserializingTypeIsDisallowed(Type) as a safety check for dangerous types. The default implementation checks the outer type name, but it does not recursively inspect array element types or generic type arguments. As a result, a type that would be blocked directly can be wrapped inside an array or constructed generic type and pass the outer type check. The formatter machinery can then materialize formatters for the inner blocked type. This vulnerability is fixed in 2.5.301 and 3.1.7.
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Affected products
MessagePack-CSharp · MessagePack-CSharpRelated CVEs — MessagePack-CSharp
In the same product, most dangerous first.
CVE-2026-92707MEDIUMMessagePack: Nested arrays can blow past buffer length limitsEPSS 0.7%CVE-2026-48109HIGHMessagePack-CSharp: LZ4 decompression may fail with AccessViolationException after dereferencing memory from bad inputEPSS 0.5%CVE-2026-48506HIGHMessagePack-CSharp: MessagePackReader.Skip can recurse without enforcing maximum object graph depthEPSS 0.5%CVE-2026-48502HIGHMessagePack-CSharp: Denial of service vulnerabilities can swamp the CPU or crash the process with stack and heap overflowsEPSS 0.4%CVE-2026-48509MEDIUMMessagePack-CSharp: ASP.NET Core MessagePackInputFormatter defaults to TrustedData for HTTP request bodiesEPSS 0.4%CVE-2026-48510MEDIUMMessagePack-CSharp: LZ4 decompression allocates from unbounded declared output lengthsEPSS 0.4%