CVE-2026-48506
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedMessagePack 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceMessagePack for C# has a vulnerability in MessagePackReader.TrySkip() which recursively descends into nested arrays/maps without proper depth tracking, bypassing MessagePackSecurity.MaximumObjectGraphDepth protection. This allows attackers to cause unbounded recursion and an uncatchable StackOverflowException via deeply nested values in positions that trigger reader.Skip() calls.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 2.5.301>= 3.0.3, < 3.1.7CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify MessagePack for C# usageSearch your project files (.csproj, packages.config, .vbproj) for a PackageReference or package entry containing 'MessagePack' from msgpack or a similar NuGet package source. Also check any direct DLL references to msgpack.dll or MessagePack.dll.Affected if MessagePack for C# library is present in the project dependencies or references.
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Determine installed MessagePack versionLocate the installed MessagePack DLL file or NuGet package version. In .NET projects, inspect the resolved version in the 'obj' folder, 'packages' folder, or via 'dotnet list package' command. The version typically appears as a 3-part number like 2.5.XXX or 3.1.XXX.Affected if The installed version is below 2.5.301, or is 3.0.3 through 3.1.6 (inclusive).
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Check if deserialization code path reaches TrySkipSearch your codebase for calls to MessagePackSerializer.Deserialize, MessagePackReader.Skip, or TrySkip methods. These are invoked when deserializing MessagePack data that may contain nested arrays or maps. Also check for any use of MessagePackSecurity.DeepSerialization() which enables depth limits.Affected if Code deserializes untrusted MessagePack data using the MessagePackReader/Deserializer APIs.
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Verify MessagePackSecurity depth limit configurationInspect your code for any MessagePackSecurity.DepthLimit or MaximumObjectGraphDepth configuration. Check if you explicitly set a depth limit via MessagePackSecurity.True depth limit settings when initializing the serializer.Affected if No explicit MessagePackSecurity depth limit is configured, or the limit is set to a very high value, making the bypass more impactful.
Your environment is affected if you use MessagePack for C# versions 2.x below 2.5.301 or 3.0.3 through 3.1.6, and your code deserializes potentially untrusted MessagePack data that could contain deeply nested arrays or maps.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped2.5.3013.1.7
Upgrade MessagePack for C# to version 2.5.301 or 3.1.7 or later to patch the recursive depth check bypass.
MessagePack-CSharp 2.5.301 (for 2.x line) or 3.1.7 (for 3.x line)
- 1. Identify the MessagePack-CSharp version currently in use by examining the project file (e.g., .csproj, packages.config, or Directory.Packages.props) or by running 'dotnet list package' in the project directory.
- 2. For projects using MessagePack version 2.x: Update the package reference to version 2.5.301 or later. In a .csproj file, change <PackageReference Include="MessagePack" Version="[old version]" /> to <PackageReference Include="MessagePack" Version="2.5.301" />, then run 'dotnet restore'.
- 3. For projects using MessagePack version 3.x: Update the package reference to version 3.1.7 or later. Change <PackageReference Include="MessagePack" Version="[old version]" /> to <PackageReference Include="MessagePack" Version="3.1.7" />, then run 'dotnet restore'.
- 4. Rebuild the solution with 'dotnet build' to ensure the new version is correctly integrated.
- 5. Run existing tests to verify the upgrade does not introduce regressions, particularly any tests involving nested object graphs or serialization/deserialization of complex structures.
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-48506 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-48506 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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