high7.5
CVE-2026-48516
MessagePack-CSharp: InterfaceLookupFormatter bypasses collision-resistant comparer settings
Impact
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
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| nuget | MessagePack | < 2.5.301 | 2.5.301 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Messagepack | Messagepack | before 2.5.301 from 3.0.3 before 3.1.7 |