CVE-2026-48506 json
MessagePack-CSharp: MessagePackReader.Skip can recurse without enforcing maximum object graph depth
published 4mo ago modified 4mo ago also GHSA-vh6j-jc39-fggf , EUVD-2026-38388
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.5%
- EPSS 0.5% chance of exploitation in 30 days, percentile 41%
- public exploits
- 0
- none known
Summary
MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePackReader.TrySkip() recursively descends into nested arrays and maps without incrementing the reader depth or calling the configured depth checks. This bypasses MessagePackSecurity.MaximumObjectGraphDepth, the library's documented protection against deeply nested object graphs. Many generated and dynamic formatters call reader.Skip() when they encounter unknown map keys, unknown array members, ignored fields, or data that should be skipped for forward compatibility. A deeply nested value in one of these skipped positions can therefore cause unbounded recursion and an uncatchable StackOverflowException. 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
Is CVE-2026-48506 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 4mo ago
Exploit prediction
0.47% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-11).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| GitHub | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
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
- Weakness
-
- CWE-674 Uncontrolled Recursion
References
-
github.com
/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-vh6j-jc39-fggf
web, mitigation, vendor-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-48506
advisory
-
github.com
/MessagePack-CSharp/MessagePack-CSharp
package
Sources
- CVE List CVE-2026-48506
- GitHub Advisory GHSA-vh6j-jc39-fggf
- NVD CVE-2026-48506
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