Vulnerability-Lookup

CVE-2026-48502 (GCVE-0-2026-48502)

Vulnerability from cvelistv5 – Published: 2026-06-22 21:18 – Updated: 2026-06-23 15:05

Title

MessagePack-CSharp: Denial of service vulnerabilities can swamp the CPU or crash the process with stack and heap overflows

Summary

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePackReader.ReadDateTime() can allocate stack memory based on an attacker-controlled MessagePack extension length. In the slow path for timestamp extension parsing, the computed tokenSize includes the extension body length from the wire and is used in a stackalloc operation before the extension length is validated as one of the valid timestamp sizes. A very small payload can claim a large timestamp extension body and cause a stack allocation large enough to trigger an uncatchable StackOverflowException, terminating the host process. This vulnerability is fixed in 2.5.301 and 3.1.7.

Severity

8.2 (High)


                        
                          CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/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 14:58 UTC

CWE

CWE-125 - Out-of-bounds Read
CWE-190 - Integer Overflow or Wraparound
CWE-407 - Inefficient Algorithmic Complexity
CWE-409 - Improper Handling of Highly Compressed Data (Data Amplification)
CWE-470 - Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')
CWE-502 - Deserialization of Untrusted Data
CWE-674 - Uncontrolled Recursion
CWE-789 - Memory Allocation with Excessive Size Value
CWE-1188 - Insecure Default Initialization of Resource

Assigner

GitHub_M mitre root

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: >= 3.1.7, < 3.1.7 Affected: < 2.5.301	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-48502

Vulnerability from fkie_nvd - Published: 2026-06-22 22:16 - Updated: 2026-06-23 17:25

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-382j-8mxh-c7x2	Mitigation, Vendor Advisory

Impacted products

	Vendor	Product	Version
	messagepack	messagepack	*
	messagepack	messagepack	*

JSON

To clipboard

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      "value": "MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePackReader.ReadDateTime() can allocate stack memory based on an attacker-controlled MessagePack extension length. In the slow path for timestamp extension parsing, the computed tokenSize includes the extension body length from the wire and is used in a stackalloc operation before the extension length is validated as one of the valid timestamp sizes. A very small payload can claim a large timestamp extension body and cause a stack allocation large enough to trigger an uncatchable StackOverflowException, terminating the host process. This vulnerability is fixed in 2.5.301 and 3.1.7."
    }
  ],
  "id": "CVE-2026-48502",
  "lastModified": "2026-06-23T17:25:05.147",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
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          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 8.2,
          "baseSeverity": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "HIGH",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
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          "options": [
            {
              "exploitation": "none"
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            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-06-23T14:58:22.893152Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-06-22T22:16:47.147",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Mitigation",
        "Vendor Advisory"
      ],
      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-382j-8mxh-c7x2"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-125"
        },
        {
          "lang": "en",
          "value": "CWE-190"
        },
        {
          "lang": "en",
          "value": "CWE-407"
        },
        {
          "lang": "en",
          "value": "CWE-409"
        },
        {
          "lang": "en",
          "value": "CWE-470"
        },
        {
          "lang": "en",
          "value": "CWE-502"
        },
        {
          "lang": "en",
          "value": "CWE-674"
        },
        {
          "lang": "en",
          "value": "CWE-789"
        },
        {
          "lang": "en",
          "value": "CWE-1188"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-382J-8MXH-C7X2

Vulnerability from github – Published: 2026-06-25 18:35 – Updated: 2026-06-25 18:35

Summary

MessagePack-CSharp: Denial of service vulnerabilities can swamp the CPU or crash the process with stack and heap overflows

Details

Summary

MessagePackReader.ReadDateTime() can allocate stack memory based on an attacker-controlled MessagePack extension length. In the slow path for timestamp extension parsing, the computed tokenSize includes the extension body length from the wire and is used in a stackalloc operation before the extension length is validated as one of the valid timestamp sizes.

A very small payload can claim a large timestamp extension body and cause a stack allocation large enough to trigger an uncatchable StackOverflowException, terminating the host process.

Impact

Applications are affected when they deserialize untrusted payloads into types containing DateTime values. This path is available through the standard formatter set and does not require opting into typeless serialization, LZ4 compression, Unity-specific resolvers, or other specialized features.

MessagePackSecurity.UntrustedData and MaximumObjectGraphDepth do not mitigate this issue because the crash is caused by a single-frame stack allocation, not by object graph recursion.

An attacker can send a MessagePack timestamp extension header with an oversized body length and insufficient body bytes. The reader enters the slow path, attempts to stack-allocate a buffer sized from that declared length, and can terminate the process before a catchable serialization exception is thrown.

Affected components

Package: MessagePack
API: MessagePackReader.ReadDateTime
Data types: DateTime and formatter paths that call ReadDateTime
Finding IDs: MESSAGEPACKCSHARP-020, related stack allocation finding MESSAGEPACKCSHARP-CROW-MEM-001

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 fix should validate timestamp extension lengths before any stack allocation. Valid MessagePack timestamp payload lengths are limited to the supported timestamp encodings, so oversized extension lengths should fail with a catchable MessagePack serialization exception before the slow path allocates a buffer.

Workarounds

Patching is recommended.

Until a patched version is available, avoid deserializing untrusted MessagePack payloads into schemas that contain DateTime or DateTimeOffset values. Where possible, enforce strict maximum message sizes and reject malformed extension payloads before they reach MessagePack-CSharp.

There is no complete workaround for applications that must deserialize attacker-controlled MessagePack data containing date/time fields with affected versions.

Resources

MESSAGEPACKCSHARP-020: ReadDateTime stack allocation from attacker-controlled extension length
MESSAGEPACKCSHARP-CROW-MEM-001: related attacker-controlled stack allocation finding in MessagePackReader
CWE-770: Allocation of Resources Without Limits or Throttling

CVE split rationale

This vulnerability is independently fixable in the DateTime extension parsing path by validating extension lengths before stack allocation. It is separate from recursive stack overflows, LZ4 issues, and collection allocation bugs.

Severity

8.2 (High)


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

Show details on source website

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To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "NuGet",
        "name": "MessagePack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0"
            },
            {
              "fixed": "3.1.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-48502"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1188",
      "CWE-125",
      "CWE-190",
      "CWE-407",
      "CWE-409",
      "CWE-470",
      "CWE-502",
      "CWE-674",
      "CWE-789"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-25T18:35:48Z",
    "nvd_published_at": "2026-06-22T22:16:47Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\n`MessagePackReader.ReadDateTime()` can allocate stack memory based on an attacker-controlled MessagePack extension length. In the slow path for timestamp extension parsing, the computed `tokenSize` includes the extension body length from the wire and is used in a `stackalloc` operation before the extension length is validated as one of the valid timestamp sizes.\n\nA very small payload can claim a large timestamp extension body and cause a stack allocation large enough to trigger an uncatchable `StackOverflowException`, terminating the host process.\n\n## Impact\n\nApplications are affected when they deserialize untrusted payloads into types containing `DateTime` values. This path is available through the standard formatter set and does not require opting into typeless serialization, LZ4 compression, Unity-specific resolvers, or other specialized features.\n\n`MessagePackSecurity.UntrustedData` and `MaximumObjectGraphDepth` do not mitigate this issue because the crash is caused by a single-frame stack allocation, not by object graph recursion.\n\nAn attacker can send a MessagePack timestamp extension header with an oversized body length and insufficient body bytes. The reader enters the slow path, attempts to stack-allocate a buffer sized from that declared length, and can terminate the process before a catchable serialization exception is thrown.\n\n## Affected components\n\n- Package: `MessagePack`\n- API: `MessagePackReader.ReadDateTime`\n- Data types: `DateTime` and formatter paths that call `ReadDateTime`\n- Finding IDs: `MESSAGEPACKCSHARP-020`, related stack allocation finding `MESSAGEPACKCSHARP-CROW-MEM-001`\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 fix should validate timestamp extension lengths before any stack allocation. Valid MessagePack timestamp payload lengths are limited to the supported timestamp encodings, so oversized extension lengths should fail with a catchable MessagePack serialization exception before the slow path allocates a buffer.\n\n## Workarounds\n\nPatching is recommended.\n\nUntil a patched version is available, avoid deserializing untrusted MessagePack payloads into schemas that contain `DateTime` or `DateTimeOffset` values. Where possible, enforce strict maximum message sizes and reject malformed extension payloads before they reach MessagePack-CSharp.\n\nThere is no complete workaround for applications that must deserialize attacker-controlled MessagePack data containing date/time fields with affected versions.\n\n## Resources\n\n- `MESSAGEPACKCSHARP-020`: `ReadDateTime` stack allocation from attacker-controlled extension length\n- `MESSAGEPACKCSHARP-CROW-MEM-001`: related attacker-controlled stack allocation finding in `MessagePackReader`\n- CWE-770: Allocation of Resources Without Limits or Throttling\n\n## CVE split rationale\n\nThis vulnerability is independently fixable in the DateTime extension parsing path by validating extension lengths before stack allocation. It is separate from recursive stack overflows, LZ4 issues, and collection allocation bugs.",
  "id": "GHSA-382j-8mxh-c7x2",
  "modified": "2026-06-25T18:35:48Z",
  "published": "2026-06-25T18:35:48Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-382j-8mxh-c7x2"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48502"
    },
    {
      "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:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "MessagePack-CSharp: Denial of service vulnerabilities can swamp the CPU or crash the process with stack and heap overflows"
}

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.

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-2026-48502 (GCVE-0-2026-48502)

FKIE_CVE-2026-48502

GHSA-382J-8MXH-C7X2

Summary

Impact

Affected components

Patches

Workarounds

Resources

CVE split rationale

Tags

Sightings

Nomenclature

Related by attack behaviour