AIKIDO-2026-845612
MessagePack is vulnerable to Denial of Service (DoS)
63
Medium Risk
This Affects:
MessagePackTL;DR
InterfaceLookupFormatter builds its internal dictionary with the default equality comparer instead of the security-aware comparer from MessagePackSecurity.UntrustedData. Untrusted payloads deserialized into ILookup can therefore trigger hash-collision CPU exhaustion even when the application opted into the untrusted-data posture. The fix creates the internal dictionary with the configured security comparer like sibling collection formatters.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and deserialize untrusted payloads into schemas containing ILookup with hash-collision-prone key types.
Background info
MessagePack is vulnerable to Denial of Service (DoS) in versions 0.0.1 - 2.5.300 and 3.0.0 - 3.1.6.
How to fix this
Upgrade the MessagePack library to the patch version.
Are You Affected?
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