CVE-2026-48517 Details
Description
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePack-CSharp's typeless deserialization includes MessagePackSerializerOptions.ThrowIfDeserializingTypeIsDisallowed(Type) as a safety check for dangerous types. The default implementation checks the outer type name, but it does not recursively inspect array element types or generic type arguments. As a result, a type that would be blocked directly can be wrapped inside an array or constructed generic type and pass the outer type check. The formatter machinery can then materialize formatters for the inner blocked type. This vulnerability is fixed in 2.5.301 and 3.1.7.
A vulnerability exists in MessagePack for C# versions prior to 2.5.301 and 3.1.7, where the typeless deserialization process does not adequately enforce type restrictions. The safety check intended to block dangerous types can be circumvented by wrapping disallowed types in arrays or generic types, allowing blocked types to be deserialized. This issue arises because the default type check only evaluates the outer type name without recursively inspecting array elements or generic type arguments. Consequently, the formatter can create formatters for the inner blocked types, potentially leading to the instantiation of harmful types in the application.
Users are advised to upgrade to MessagePack versions 2.5.301 or 3.1.7. If typeless deserialization of untrusted data is necessary, configure an explicit allowlist that recursively validates array elements and generic arguments, rejecting any type not approved by the application.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 23, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-qhmf-xw27-6rqr | [email protected] | MitigationVendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-470 | Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') | [email protected] |
| CWE-502 | Deserialization of Untrusted Data | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| messagepack messagepack | < 2.5.301 >= 3.0.3, < 3.1.7 |
CPE
Remediation
| |
Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 25, 2026 | CVE Modified | [email protected] |
| Jun 23, 2026 | Initial Analysis | [email protected] |
| Jun 23, 2026 | CVE Modified | CISA-ADP |
| Jun 22, 2026 | New CVE Received | [email protected] |