AIKIDO-2026-388295
MessagePack is vulnerable to Denial of Service (DoS)
63
Medium Risk
This Affects:
MessagePackTL;DR
ExpandoObjectFormatter inserts each map entry with IDictionary.Add, and ExpandoObject performs repeated linear scans as keys grow. Large attacker-controlled maps can therefore cause quadratic CPU and allocation work even when MessagePackSecurity.UntrustedData is enabled. The fix applies untrusted-data map entry limits and rejects oversized maps before quadratic insertion work begins.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and deserialize untrusted MessagePack maps into ExpandoObject.
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.
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SOC 2Compliant
ISO 27001CompliantISO 42001Compliant
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