CVE-2026-48516
Published:June 22, 2026
Updated:June 26, 2026
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.
Affected Packages
MessagePack (DOT_NET):
Affected version(s) >=0.0.0.0 <2.5.301Fix Suggestion:
Update to version 2.5.301MessagePack (DOT_NET):
Affected version(s) >=3.0.3.6 <3.1.7Fix Suggestion:
Update to version 3.1.7messagepack (NUGET):
Affected version(s) >=0.1.0-beta <2.5.301Fix Suggestion:
Update to version 2.5.301messagepack (NUGET):
Affected version(s) >=3.0.3 <3.1.7Fix Suggestion:
Update to version 3.1.7Related Resources (1)
Do you need more information?
Contact UsCVSS v4
Base Score:
6.3
Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
LOW
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
3.7
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
LOW
Weakness Type (CWE)
Inefficient Algorithmic Complexity
EPSS
Base Score:
0.23