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TI-2026-35866 Aliases CVE-2026-48506GHSA-vh6j-jc39-fggf

MessagePack-CSharp: MessagePackReader.Skip can recurse without enforcing maximum object graph depth

Priority LOW 39CWE-674Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-674.

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00471 41st percentileScored 2026-11-07
Fix Fixed MessagePack-CSharp (MessagePack-CSharp): 3.1.7, 2.5.301MessagePack (NuGet): 2.5.301, 3.1.7

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MessagePack-CSharpMessagePack-CSharp3.1.7 to before 3.1.7; before 2.5.3013.1.7, 2.5.301Patch availableCNA
—MessagePack (NuGet)before 2.5.3012.5.301Patch availableGHSA-vh6j-jc39-fggf
—MessagePack (NuGet)3.0 to before 3.1.73.1.7Patch availableGHSA-vh6j-jc39-fggf
  • MessagePack-CSharp VendorMessagePack-CSharp Affected 3.1.7 to before 3.1.7; before 2.5.301 Fixed in 3.1.7, 2.5.301 Patch available CNA
  • MessagePack (NuGet) Vendor— Affected before 2.5.301 Fixed in 2.5.301 Patch available GHSA-vh6j-jc39-fggf
  • MessagePack (NuGet) Vendor— Affected 3.0 to before 3.1.7 Fixed in 3.1.7 Patch available GHSA-vh6j-jc39-fggf

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\#:*:*before 2.5.301; 3.0.3 to before 3.1.7VulnerableMessagePack-CSharp
  • cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\#:*:* Versions before 2.5.301; 3.0.3 to before 3.1.7 Vulnerable ·MessagePack-CSharp

Remediation

  • Fix · CNA MessagePack-CSharp (MessagePack-CSharp) Fixed in 3.1.7, 2.5.301
  • Fix · GHSA-vh6j-jc39-fggf MessagePack (NuGet) Fixed in 2.5.301 Advisory →
  • Fix · GHSA-vh6j-jc39-fggf MessagePack (NuGet) Fixed in 3.1.7 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-48506
  2. 2026-10-03 Alias added: GHSA-vh6j-jc39-fggf

References

Advisory 2

Other 1

  • TI-2026-35549 MessagePack-CSharp: LZ4 decompression may fail with AccessViolationException after dereferencing memory from bad input CVSS 3.1HIGH 8.2
  • TI-2026-35873 MessagePack-CSharp: DynamicUnionResolver generated deserializers miss depth enforcement CVSS 4.0MEDIUM 6.3
  • TI-2026-35863 Out-of-bounds read in MessagePack-CSharp CVSS 4.0HIGH 8.2
  • TI-2020-04290 Untrusted data can lead to DoS attack in MessagePack for C# and Unity CVSS 3.1MEDIUM 6.5
  • TI-2026-35877 MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments CVSS 4.0MEDIUM 6.3
  • TI-2026-35876 MessagePack-CSharp: InterfaceLookupFormatter bypasses collision-resistant comparer settings CVSS 4.0MEDIUM 6.3
See all 12 →

Sources

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