CVE-2026-48517 json
MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments
published 2026-06-22 4 mo ago modified 2026-06-25 4 mo ago also GHSA-qhmf-xw27-6rqr , EUVD-2026-38363
- cvss
- 7.5
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 28%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- nuget MessagePack 2.5.301, 3.1.7
- messagepack messagepack 2.5.301, 3.1.7
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 4 mo ago
Exploit prediction
0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 6.3 | CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N |
| CNA | 4.0 | 6.3 | CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| NVD | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| nuget | MessagePack | <2.5.301 >=3.0, <3.1.7 |
2.5.301 3.1.7 |
Affected products
- MessagePack-CSharp MessagePack-CSharp
Classification
References
-
github.com
/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-qhmf-xw27-6rqr
web, mitigation, vendor-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-48517
advisory
-
github.com
/MessagePack-CSharp/MessagePack-CSharp
package
Sources
- CVE List CVE-2026-48517
- GitHub Advisory GHSA-qhmf-xw27-6rqr
- NVD CVE-2026-48517
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