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CVE-2026-92707

Status: Awaiting AnalysisMedium (5.3)—
Severity5.3Medium · CVSS 3.1
Exploitation probability0.65 %higher than 50% of CVEs
Active exploitationNonot in the CISA catalog
Public exploitNot knownno public code found

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.303 and 3.1.9, deserializing attacker-controlled MessagePack data as System.Object through PrimitiveObjectFormatter can cause excessive memory allocation. The formatter allocates an object[] from each declared array length before the configured object-graph depth limit rejects the input, while nested array headers can reuse the same trailing unread bytes to satisfy per-header length validation. A comparatively small payload can therefore keep many large arrays alive at once.

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When an attacker can submit such data repeatedly, the allocations can cause severe managed-heap pressure, excessive garbage collection, process termination, or loss of service. Exposure requires an application to deserialize untrusted data through the affected formatter path and permit repeated attacker-controlled submissions, such as a reachable ASP.NET Core SignalR hub method with an object parameter and AddMessagePackProtocol() enabled. This issue is fixed in versions 2.5.303 and 3.1.9.

CVSS

Base score
5.3
Version
3.1
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days
0.65 %
Percentile among all scored CVEs
50
Score date
10/20/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

El vector AV:N/PR:N/UI:N permite explotación remota sin autenticación; deserializar datos controlados asigna arrays grandes que agotan el heap y provocan pérdida de servicio.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

ATT&CK mitigations that cover these techniques

Filter Network TrafficVulnerability ScanningPrivileged Account ManagementNetwork SegmentationLimit Access to Resource Over NetworkApplication Isolation and Sandboxing

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Microsoft — Messagepack CsharpAI

CWEs

References

Show 5 references

Raw JSON (NVD)

Show
{
  "id": "CVE-2026-92707",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-92707",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-10-15T20:10:28.719217Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "security-advisories@github.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.3,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "LOW",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "security-advisories@github.com",
      "affectedData": [
        {
          "vendor": "MessagePack-CSharp",
          "product": "MessagePack-CSharp",
          "versions": [
            {
              "status": "affected",
              "version": "< 2.5.303"
            },
            {
              "status": "affected",
              "version": ">= 3.0.0, < 3.1.9"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-10-15T19:17:48.703",
  "references": [
    {
      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/commit/7fd78bbf3476e03beae8b0f7a521125525a8a64a",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/commit/95b63fca4f7097d3cac12d1a95286af4b4bbf02c",
      "source": "security-advisories@github.com"
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      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v2.5.303",
      "source": "security-advisories@github.com"
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      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/releases/tag/v3.1.9",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-qhrr-8q5h-9q3h",
      "source": "security-advisories@github.com"
    }
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  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security-advisories@github.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-1325"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.303 and 3.1.9, deserializing attacker-controlled MessagePack data as System.Object through PrimitiveObjectFormatter can cause excessive memory allocation. The formatter allocates an object[] from each declared array length before the configured object-graph depth limit rejects the input, while nested array headers can reuse the same trailing unread bytes to satisfy per-header length validation. A comparatively small payload can therefore keep many large arrays alive at once. When an attacker can submit such data repeatedly, the allocations can cause severe managed-heap pressure, excessive garbage collection, process termination, or loss of service. Exposure requires an application to deserialize untrusted data through the affected formatter path and permit repeated attacker-controlled submissions, such as a reachable ASP.NET Core SignalR hub method with an object parameter and AddMessagePackProtocol() enabled. This issue is fixed in versions 2.5.303 and 3.1.9."
    }
  ],
  "lastModified": "2026-10-16T16:00:33.533",
  "sourceIdentifier": "security-advisories@github.com"
}