CVE-2026-108859 (GCVE-0-2026-108859)

Vulnerability from cvelistv5 – Published: 2026-10-11 13:26 – Updated: 2026-10-11 13:26
VLAI
Title
mcp-go through 1.2.1 Denial of Service via Unbounded POST Body Buffering
Summary
mcp-go through 1.2.1 contains a denial of service vulnerability in StreamableHTTPServer.ServeHTTP that allows remote unauthenticated attackers to exhaust memory by sending oversized POST bodies. Attackers can send arbitrarily large or many concurrent POST requests, read fully via io.ReadAll before validation, to degrade or OOM-kill the server process.
Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
  • CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
VulnCheck CNA under the mitre root
CNA scorecard B 84/100 over 5947 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
mark3labs mcp-go Affected: 0 , ≤ 1.2.1 (semver)
guessed Create a notification for this product.
Date Public
2026-10-11 00:00
Credits
hieuPenguinnn
Show details on NVD website
To clipboard 

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              "version": "0",
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      "providerMetadata": {
        "dateUpdated": "2026-10-11T13:26:06.450Z",
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck"
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          "url": "https://hackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/mark3labs-mcp-go-streamable-http-unbounded-body"
        },
        {
          "tags": [
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          "url": "https://github.com/mark3labs/mcp-go/blob/90d247ed8d45cbb7d71d9a95e112789b78760443/server/streamable_http.go#L405-L411"
        },
        {
          "tags": [
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          "url": "https://github.com/mark3labs/mcp-go"
        },
        {
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          "tags": [
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        }
      ],
      "title": "mcp-go through 1.2.1 Denial of Service via Unbounded POST Body Buffering",
      "x_generator": {
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  "cveMetadata": {
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2026-108859",
    "datePublished": "2026-10-11T13:26:06.450Z",
    "dateReserved": "2026-10-11T13:06:49.278Z",
    "dateUpdated": "2026-10-11T13:26:06.450Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
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      "date": "2026-10-13",
      "epss": "0.00545",
      "percentile": "0.44229"
    },
    "nvd": {
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                "defaultStatus": "unaffected",
                "packageURL": "pkg:golang/github.com/mark3labs/mcp-go",
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                "vendor": "mark3labs",
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          }
        ],
        "id": "CVE-2026-108859",
        "lastModified": "2026-10-11T14:17:05.893",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
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                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
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                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
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          ],
          "cvssMetricV40": [
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                "availabilityRequirement": "NOT_DEFINED",
                "baseScore": 8.7,
                "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:L/AT:N/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",
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        "references": [
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            "url": "https://github.com/mark3labs/mcp-go"
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            "source": "disclosure@vulncheck.com",
            "url": "https://github.com/mark3labs/mcp-go/blob/90d247ed8d45cbb7d71d9a95e112789b78760443/server/streamable_http.go#L405-L411"
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    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-10-12T04:12:05+00:00",
      "cve": "CVE-2026-108859",
      "id": "CVE-2026-108859",
      "initial_release_date": "2026-10-11T13:26:06.450000+00:00",
      "product_status:known_affected": "7",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "github.com/mark3labs/mcp-go: mcp-go: Denial of Service via unbounded HTTP request body buffering",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-108859.json",
      "version": "3"
    }
  }
}



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