Vulnerability-Lookup

CVE-2026-48512 (GCVE-0-2026-48512)

Vulnerability from cvelistv5 – Published: 2026-06-22 21:14 – Updated: 2026-06-25 15:16

Title

MessagePack-CSharp: JSON conversion APIs can recurse without consistent depth enforcement

Summary

MessagePack 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.

Severity

6.3 (Medium)


                        
                          CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-23 14:56 UTC

CWE

CWE-674 - Uncontrolled Recursion

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7886 records in the last 180 days details

References

1 reference

URL	Tags
https://github.com/MessagePack-CSharp/MessagePack…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version	CPE status
MessagePack-CSharp	MessagePack-CSharp	Affected: >= 3.0, < 3.1.7 Affected: < 2.5.301	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-48512

Vulnerability from fkie_nvd - Published: 2026-06-22 22:16 - Updated: 2026-06-25 16:16

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-cj9g-3mj2-g8vv	Mitigation, Vendor Advisory

Impacted products

	Vendor	Product	Version
	messagepack	messagepack	*
	messagepack	messagepack	*

JSON

To clipboard

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            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-06-23T14:56:50.903334Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-06-22T22:16:47.970",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Mitigation",
        "Vendor Advisory"
      ],
      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-cj9g-3mj2-g8vv"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-674"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-CJ9G-3MJ2-G8VV

Vulnerability from github – Published: 2026-06-25 19:51 – Updated: 2026-06-25 19:51

Summary

MessagePack-CSharp: JSON conversion APIs can recurse without consistent depth enforcement

Details

Summary

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.

Three related issues are covered by this advisory:

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.

Impact

Applications are affected when they call MessagePack-CSharp JSON conversion APIs on attacker-controlled data. This includes gateways, diagnostics endpoints, migration tools, logging paths, and services that convert between external JSON and MessagePack payloads.

For JSON-to-MessagePack conversion, deeply nested JSON arrays or objects can recurse through FromJsonCore() without applying the configured object graph depth limit. Separately, long runs of comma or colon separator characters can recurse through TinyJsonReader.ReadNextToken() before normal structural validation rejects the input.

For MessagePack-to-JSON conversion, nested typeless extension wrappers can recurse through ToJsonCore() without the depth guard that the same function applies to arrays and maps.

MessagePackSecurity.UntrustedData does not fully mitigate these conversion paths because the missing checks occur inside JSON conversion and tokenization branches that do not consistently use the configured depth policy.

Affected components

Package: MessagePack
APIs: MessagePackSerializer.ConvertFromJson, MessagePackSerializer.ConvertToJson
Internal routines: FromJsonCore, ToJsonCore, TinyJsonReader.ReadNextToken
Data shapes: deeply nested JSON arrays/objects, long JSON separator runs, and nested typeless MessagePack extension values converted to JSON
Finding IDs: MESSAGEPACKCSHARP-090, MESSAGEPACKCSHARP-091, MESSAGEPACKCSHARP-092

Patches

Fixes are prepared and will be released in coordinated patch versions.

Upgrade guidance:

Upgrade MessagePack to the patched version for your release line.
Upgrade companion MessagePack packages in the same dependency graph to the coordinated patched versions.

The JSON-to-MessagePack fix should add explicit JSON nesting-depth accounting to FromJsonCore, using the configured maximum object graph depth or an equivalent limit, or rewrite the conversion to use an iterative bounded stack.

The tokenizer fix should replace separator self-recursion in TinyJsonReader.ReadNextToken() with an iterative loop so consecutive commas, colons, and whitespace do not consume stack frames.

The MessagePack-to-JSON fix should apply DepthStep and matching reader.Depth-- cleanup around recursive ToJsonCore() calls made from the typeless extension branch, consistent with the existing array and map conversion branches.

Workarounds

Patching is recommended.

Until a patched version is available, do not pass untrusted JSON directly to ConvertFromJson, and do not call ConvertToJson on untrusted MessagePack payloads that may contain typeless extension values. Validate JSON nesting depth with a parser that enforces depth limits before calling MessagePack-CSharp, reject malformed JSON before conversion, and apply strict input-size limits.

Input-size limits reduce exposure but do not remove the recursive behavior in affected versions.

References

MESSAGEPACKCSHARP-090: ConvertFromJson unbounded structural recursion
MESSAGEPACKCSHARP-091: TinyJsonReader.ReadNextToken separator self-recursion
MESSAGEPACKCSHARP-092: ConvertToJson ext-100 branch missing depth enforcement
CWE-674: Uncontrolled Recursion

CVE split rationale

These issues are grouped because they affect the same JSON conversion feature area and share the same failure mode: recursive conversion/tokenization paths do not consistently enforce depth or iteration bounds for attacker-controlled input. They are distinct from normal binary MessagePack skip recursion, dynamic union formatter depth accounting, DateTime stack allocation, and allocation-oriented denial-of-service issues.

Severity

6.3 (Medium)


                  
                    CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "NuGet",
        "name": "MessagePack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.5.301"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "NuGet",
        "name": "MessagePack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0"
            },
            {
              "fixed": "3.1.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-48512"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-25T19:51:36Z",
    "nvd_published_at": "2026-06-22T22:16:47Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nMessagePack-CSharp\u0027s 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.\n\nThree related issues are covered by this advisory:\n\n1. `MessagePackSerializer.ConvertFromJson` recursively processes nested JSON arrays and objects in `FromJsonCore()` without consulting `MessagePackSecurity.MaximumObjectGraphDepth`.\n2. `TinyJsonReader.ReadNextToken()` recursively consumes comma and colon separator characters, allowing even malformed JSON with long separator runs to consume one stack frame per character.\n3. `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)`.\n\nEach 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.\n\n## Impact\n\nApplications are affected when they call MessagePack-CSharp JSON conversion APIs on attacker-controlled data. This includes gateways, diagnostics endpoints, migration tools, logging paths, and services that convert between external JSON and MessagePack payloads.\n\nFor JSON-to-MessagePack conversion, deeply nested JSON arrays or objects can recurse through `FromJsonCore()` without applying the configured object graph depth limit. Separately, long runs of comma or colon separator characters can recurse through `TinyJsonReader.ReadNextToken()` before normal structural validation rejects the input.\n\nFor MessagePack-to-JSON conversion, nested typeless extension wrappers can recurse through `ToJsonCore()` without the depth guard that the same function applies to arrays and maps.\n\n`MessagePackSecurity.UntrustedData` does not fully mitigate these conversion paths because the missing checks occur inside JSON conversion and tokenization branches that do not consistently use the configured depth policy.\n\n## Affected components\n\n- Package: `MessagePack`\n- APIs: `MessagePackSerializer.ConvertFromJson`, `MessagePackSerializer.ConvertToJson`\n- Internal routines: `FromJsonCore`, `ToJsonCore`, `TinyJsonReader.ReadNextToken`\n- Data shapes: deeply nested JSON arrays/objects, long JSON separator runs, and nested typeless MessagePack extension values converted to JSON\n- Finding IDs: `MESSAGEPACKCSHARP-090`, `MESSAGEPACKCSHARP-091`, `MESSAGEPACKCSHARP-092`\n\n## Patches\n\nFixes are prepared and will be released in coordinated patch versions.\n\nUpgrade guidance:\n\n1. Upgrade `MessagePack` to the patched version for your release line.\n2. Upgrade companion MessagePack packages in the same dependency graph to the coordinated patched versions.\n\nThe JSON-to-MessagePack fix should add explicit JSON nesting-depth accounting to `FromJsonCore`, using the configured maximum object graph depth or an equivalent limit, or rewrite the conversion to use an iterative bounded stack.\n\nThe tokenizer fix should replace separator self-recursion in `TinyJsonReader.ReadNextToken()` with an iterative loop so consecutive commas, colons, and whitespace do not consume stack frames.\n\nThe MessagePack-to-JSON fix should apply `DepthStep` and matching `reader.Depth--` cleanup around recursive `ToJsonCore()` calls made from the typeless extension branch, consistent with the existing array and map conversion branches.\n\n## Workarounds\n\nPatching is recommended.\n\nUntil a patched version is available, do not pass untrusted JSON directly to `ConvertFromJson`, and do not call `ConvertToJson` on untrusted MessagePack payloads that may contain typeless extension values. Validate JSON nesting depth with a parser that enforces depth limits before calling MessagePack-CSharp, reject malformed JSON before conversion, and apply strict input-size limits.\n\nInput-size limits reduce exposure but do not remove the recursive behavior in affected versions.\n\n## References\n\n- `MESSAGEPACKCSHARP-090`: `ConvertFromJson` unbounded structural recursion\n- `MESSAGEPACKCSHARP-091`: `TinyJsonReader.ReadNextToken` separator self-recursion\n- `MESSAGEPACKCSHARP-092`: `ConvertToJson` ext-100 branch missing depth enforcement\n- CWE-674: Uncontrolled Recursion\n\n## CVE split rationale\n\nThese issues are grouped because they affect the same JSON conversion feature area and share the same failure mode: recursive conversion/tokenization paths do not consistently enforce depth or iteration bounds for attacker-controlled input. They are distinct from normal binary MessagePack skip recursion, dynamic union formatter depth accounting, DateTime stack allocation, and allocation-oriented denial-of-service issues.",
  "id": "GHSA-cj9g-3mj2-g8vv",
  "modified": "2026-06-25T19:51:36Z",
  "published": "2026-06-25T19:51:36Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-cj9g-3mj2-g8vv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48512"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "MessagePack-CSharp: JSON conversion APIs can recurse without consistent depth enforcement"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-48512 (GCVE-0-2026-48512)

FKIE_CVE-2026-48512

GHSA-CJ9G-3MJ2-G8VV

Summary

Impact

Affected components

Patches

Workarounds

References

CVE split rationale

Tags

Sightings

Nomenclature

Vulnerability timeline

Related by attack behaviour