CVE-2026-48512
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, MessagePack-CSharp's JSON conversion helpers contain multiple recursion paths that do not consistently enforce a depth limit. These paths are in the JSON conversion component rather than normal typed MessagePack deserialization. MessagePackSerializer.ConvertFromJson recursively processes nested JSON arrays and objects in FromJsonCore() without consulting MessagePackSecurity.MaximumObjectGraphDepth. TinyJsonReader.ReadNextToken() recursively consumes comma and colon separator characters, allowing even malformed JSON with long separator runs to consume one stack frame per character. MessagePackSerializer.ConvertToJson applies depth checks to arrays and maps, but the typeless extension branch for ext-100 recursively calls ToJsonCore() without applying MessagePackSecurity.DepthStep(ref reader). Each path can allow attacker-controlled input to exhaust the process stack and trigger an uncatchable StackOverflowException instead of failing with a catchable parse or serialization exception. 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-CSharp's JSON conversion helpers contain multiple recursion paths that bypass depth limits. Specifically, FromJsonCore() doesn't consult MaximumObjectGraphDepth, TinyJsonReader.ReadNextToken() recursively consumes separators allowing stack exhaustion one frame at a time, and ConvertToJson's typeless extension branch calls ToJsonCore() without DepthStep(). These paths allow attacker-controlled nested JSON to trigger an uncatchable StackOverflowException.
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 installed MessagePack-CSharp versionCheck your project dependencies (packages.config, .csproj, or package manager) for the MessagePack package version. If using a compiled binary, examine the assembly version attribute.Affected if Version is less than 2.5.301, or between 3.0.3 and 3.1.7 (exclusive of 3.1.7)
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Verify JSON conversion feature usageSearch your codebase for calls to any JSON conversion methods provided by MessagePack-CSharp, such as ConvertToJson, FromJson, ToJson, or usage of JsonReader/JsonWriter classes.Affected if Your application directly uses MessagePack-CSharp JSON serialization/deserialization methods on untrusted input
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Inspect MaximumObjectGraphDepth configurationCheck your MessagePack serializer configuration for any explicit setting of MaximumObjectGraphDepth (or similar depth-limiting options). Note that the vulnerability exists because certain paths ignore this setting.Affected if The depth limit is not set or is set to a high value, and untrusted nested JSON is processed
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Examine TinyJsonReader implementationIf you have access to the source code, look for the TinyJsonReader class and its ReadNextToken method to verify if recursive separator handling is present.Affected if The vulnerable TinyJsonReader code path is in use and processes attacker-controlled nested JSON structures
Your environment is affected if you use a vulnerable version of MessagePack-CSharp (below 2.5.301 or between 3.0.3 and 3.1.7) AND process untrusted JSON input through the MessagePack JSON conversion helpers.
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 to MessagePack-CSharp version 2.5.301 or 3.1.7 which contain the fix for consistent depth limit enforcement across all JSON conversion paths.
2.5.301 (for 2.x users) or 3.1.7 (for 3.x users)
- 1. Identify your current MessagePack-CSharp version by checking your .csproj file or packages.config for 'MessagePack' package reference
- 2. If using version 2.x (before 2.5.301), update the package reference to version 2.5.301 or later
- 3. If using version 3.x (3.0.3 to 3.1.6), update the package reference to version 3.1.7 or later
- 4. Update the package using your NuGet package manager: 'Update-Package MessagePack' or edit the .csproj version manually
- 5. Rebuild your solution to ensure the new version is integrated
- 6. Run your application's test suite to verify JSON conversion functionality works correctly
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation6.0 h
- Testing5.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-48512 — 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-2026-48512 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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