vulnerability / NVI-00017614 / Revision 1
MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments
GitHub lists this reviewed advisory for MessagePack, MessagePack. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
MessagePack
source listed< 2.5.301
## Summary 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. ## Impact Applications are affected when they deserialize untrusted payloads using typeless serialization features such as `MessagePackSerializer.Typeless`, `TypelessObjectResolver`, or related typeless resolver options. Typeless deserialization is already a high-risk feature for untrusted data, but the presence of a disallowed-type hook creates an expectation that blocked types remain blocked. This issue weakens that mitigation because the check is not applied structurally to nested type components. An attacker who can supply typeless ext-100 payloads may bypass exact outer-type blocklist checks by naming wrapper types such as arrays or generic
MessagePack
source listed>= 3.0, < 3.1.7
## Summary 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. ## Impact Applications are affected when they deserialize untrusted payloads using typeless serialization features such as `MessagePackSerializer.Typeless`, `TypelessObjectResolver`, or related typeless resolver options. Typeless deserialization is already a high-risk feature for untrusted data, but the presence of a disallowed-type hook creates an expectation that blocked types remain blocked. This issue weakens that mitigation because the check is not applied structurally to nested type components. An attacker who can supply typeless ext-100 payloads may bypass exact outer-type blocklist checks by naming wrapper types such as arrays or generic
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-qhmf-xw27-6rqr ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.