Vulnerability Details CVE-2026-48516
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, InterfaceLookupFormatter<TKey,TElement> constructs an internal Dictionary<TKey, IGrouping<TKey,TElement>> with the default equality comparer instead of the security-aware comparer supplied by options.Security.GetEqualityComparer<TKey>(). This formatter omission allows hash-collision CPU denial of service against ILookup<TKey,TElement> even when the application has opted into the untrusted-data security posture This vulnerability is fixed in 2.5.301 and 3.1.7.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.002
EPSS Ranking 10.8%
CVSS Severity
CVSS v3 Score 7.5
Products affected by CVE-2026-48516
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cpe:2.3:a:messagepack:messagepack:.1.7.3.5
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cpe:2.3:a:messagepack:messagepack:.1.7.3.6
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cpe:2.3:a:messagepack:messagepack:1.0.1
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cpe:2.3:a:messagepack:messagepack:1.0.2
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cpe:2.3:a:messagepack:messagepack:1.0.3
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cpe:2.3:a:messagepack:messagepack:1.1.0
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cpe:2.3:a:messagepack:messagepack:1.1.1
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cpe:2.3:a:messagepack:messagepack:1.1.2
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cpe:2.3:a:messagepack:messagepack:1.2.0
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cpe:2.3:a:messagepack:messagepack:1.2.1
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cpe:2.3:a:messagepack:messagepack:1.2.3
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cpe:2.3:a:messagepack:messagepack:1.3.0
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cpe:2.3:a:messagepack:messagepack:1.3.1
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cpe:2.3:a:messagepack:messagepack:1.3.2
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cpe:2.3:a:messagepack:messagepack:1.3.3
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cpe:2.3:a:messagepack:messagepack:1.4.0
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cpe:2.3:a:messagepack:messagepack:1.4.1
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cpe:2.3:a:messagepack:messagepack:1.4.2
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cpe:2.3:a:messagepack:messagepack:1.4.3
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cpe:2.3:a:messagepack:messagepack:1.4.4
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cpe:2.3:a:messagepack:messagepack:1.5.0
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cpe:2.3:a:messagepack:messagepack:1.5.1
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cpe:2.3:a:messagepack:messagepack:1.6.0
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cpe:2.3:a:messagepack:messagepack:1.6.1
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cpe:2.3:a:messagepack:messagepack:1.6.1.2
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cpe:2.3:a:messagepack:messagepack:1.6.2
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cpe:2.3:a:messagepack:messagepack:1.7.0
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cpe:2.3:a:messagepack:messagepack:1.7.1
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cpe:2.3:a:messagepack:messagepack:1.7.2
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cpe:2.3:a:messagepack:messagepack:1.7.3
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cpe:2.3:a:messagepack:messagepack:1.7.3.1
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cpe:2.3:a:messagepack:messagepack:1.7.3.2
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cpe:2.3:a:messagepack:messagepack:1.7.3.3
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cpe:2.3:a:messagepack:messagepack:1.7.3.4
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cpe:2.3:a:messagepack:messagepack:1.7.3.7
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cpe:2.3:a:messagepack:messagepack:1.9.3
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cpe:2.3:a:messagepack:messagepack:2.0.110
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cpe:2.3:a:messagepack:messagepack:2.0.119
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cpe:2.3:a:messagepack:messagepack:2.0.123
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cpe:2.3:a:messagepack:messagepack:2.0.204
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cpe:2.3:a:messagepack:messagepack:2.0.270
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cpe:2.3:a:messagepack:messagepack:2.0.299
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cpe:2.3:a:messagepack:messagepack:2.0.323
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cpe:2.3:a:messagepack:messagepack:2.0.335
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cpe:2.3:a:messagepack:messagepack:2.0.94
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cpe:2.3:a:messagepack:messagepack:2.1.115
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cpe:2.3:a:messagepack:messagepack:2.1.143
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cpe:2.3:a:messagepack:messagepack:2.1.152
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cpe:2.3:a:messagepack:messagepack:2.1.165
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cpe:2.3:a:messagepack:messagepack:2.1.194
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cpe:2.3:a:messagepack:messagepack:2.1.80
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cpe:2.3:a:messagepack:messagepack:2.1.90
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cpe:2.3:a:messagepack:messagepack:2.2.113
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cpe:2.3:a:messagepack:messagepack:2.2.36
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cpe:2.3:a:messagepack:messagepack:2.2.44
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cpe:2.3:a:messagepack:messagepack:2.2.60
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cpe:2.3:a:messagepack:messagepack:2.2.85
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cpe:2.3:a:messagepack:messagepack:2.3.112
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cpe:2.3:a:messagepack:messagepack:2.3.58
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cpe:2.3:a:messagepack:messagepack:2.3.73
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cpe:2.3:a:messagepack:messagepack:2.3.75
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cpe:2.3:a:messagepack:messagepack:2.3.85
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cpe:2.3:a:messagepack:messagepack:2.4.14
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cpe:2.3:a:messagepack:messagepack:2.4.23
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cpe:2.3:a:messagepack:messagepack:2.4.35
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cpe:2.3:a:messagepack:messagepack:2.4.59
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cpe:2.3:a:messagepack:messagepack:2.5.103
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cpe:2.3:a:messagepack:messagepack:2.5.108
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cpe:2.3:a:messagepack:messagepack:2.5.124
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cpe:2.3:a:messagepack:messagepack:2.5.129
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cpe:2.3:a:messagepack:messagepack:2.5.140
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cpe:2.3:a:messagepack:messagepack:2.5.168
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cpe:2.3:a:messagepack:messagepack:2.5.171
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cpe:2.3:a:messagepack:messagepack:2.5.172
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cpe:2.3:a:messagepack:messagepack:2.5.187
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cpe:2.3:a:messagepack:messagepack:2.5.192
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cpe:2.3:a:messagepack:messagepack:2.5.198
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cpe:2.3:a:messagepack:messagepack:2.5.205
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cpe:2.3:a:messagepack:messagepack:2.5.64
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cpe:2.3:a:messagepack:messagepack:2.5.94
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cpe:2.3:a:messagepack:messagepack:3.0.111
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cpe:2.3:a:messagepack:messagepack:3.0.129
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cpe:2.3:a:messagepack:messagepack:3.0.134
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cpe:2.3:a:messagepack:messagepack:3.0.208
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cpe:2.3:a:messagepack:messagepack:3.0.214
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cpe:2.3:a:messagepack:messagepack:3.0.233
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cpe:2.3:a:messagepack:messagepack:3.0.238
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cpe:2.3:a:messagepack:messagepack:3.0.3
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cpe:2.3:a:messagepack:messagepack:3.0.300
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cpe:2.3:a:messagepack:messagepack:3.0.301
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cpe:2.3:a:messagepack:messagepack:3.0.54
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cpe:2.3:a:messagepack:messagepack:3.1.0
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cpe:2.3:a:messagepack:messagepack:3.1.1
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cpe:2.3:a:messagepack:messagepack:3.1.2
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cpe:2.3:a:messagepack:messagepack:3.1.3
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cpe:2.3:a:messagepack:messagepack:3.1.4
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cpe:2.3:a:messagepack:messagepack:3.1.5
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cpe:2.3:a:messagepack:messagepack:3.1.6