Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') Affecting messagepack package, versions [3.0,3.1.7)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-DOTNET-MESSAGEPACK-17660972
- published28 Jun 2026
- disclosed25 Jun 2026
- creditUnknown
Introduced: 25 Jun 2026
NewCVE-2026-48502 (opens in a new tab)How to fix?
Upgrade MessagePack to version 3.1.7 or higher.
Overview
MessagePack is a MessagePack(MsgPack) Serializer for C#(.NET, .NET Core, Unity, Xamarin).
Affected versions of this package are vulnerable to Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') in the ReadDateTime function when processing a MessagePack timestamp extension with an attacker-controlled extension length. An attacker can cause the process to terminate unexpectedly by sending a crafted payload that triggers a large stack allocation, resulting in an uncatchable stack overflow exception before proper validation occurs. This is only exploitable if untrusted MessagePack data containing date/time fields is deserialized.
Workaround
This vulnerability can be mitigated by avoiding deserialization of untrusted MessagePack payloads containing date/time fields and enforcing strict maximum message sizes or rejecting malformed extension payloads before processing.