{
  "document": {
    "acknowledgments": [
      {
        "names": [
          "Michal Kamensky with Microsoft"
        ]
      }
    ],
    "aggregate_severity": {
      "namespace": "https://www.microsoft.com/en-us/msrc/security-update-severity-rating-system",
      "text": "Important"
    },
    "category": "csaf_security_advisory",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Public",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en-US",
    "notes": [
      {
        "category": "general",
        "text": "To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle",
        "title": "Additional Resources"
      },
      {
        "category": "legal_disclaimer",
        "text": "The information provided in the Microsoft Knowledge Base is provided \\\"as is\\\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.",
        "title": "Disclaimer"
      },
      {
        "category": "general",
        "text": "Required. The vulnerability documented by this CVE requires customer action to resolve.",
        "title": "Customer Action"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "secure@microsoft.com",
      "name": "Microsoft Security Response Center",
      "namespace": "https://msrc.microsoft.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "CVE-2026-21537 Microsoft Defender for Endpoint Linux Extension Remote Code Execution Vulnerability - HTML",
        "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21537"
      },
      {
        "category": "self",
        "summary": "CVE-2026-21537 Microsoft Defender for Endpoint Linux Extension Remote Code Execution Vulnerability - CSAF",
        "url": "https://msrc.microsoft.com/csaf/advisories/2026/msrc_cve-2026-21537.json"
      },
      {
        "category": "external",
        "summary": "Microsoft Exploitability Index",
        "url": "https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1"
      },
      {
        "category": "external",
        "summary": "Microsoft Support Lifecycle",
        "url": "https://support.microsoft.com/lifecycle"
      },
      {
        "category": "external",
        "summary": "Common Vulnerability Scoring System",
        "url": "https://www.first.org/cvss"
      }
    ],
    "title": "Microsoft Defender for Endpoint Linux Extension Remote Code Execution Vulnerability",
    "tracking": {
      "current_release_date": "2026-02-10T08:00:00.000Z",
      "generator": {
        "date": "2026-02-10T18:57:59.800Z",
        "engine": {
          "name": "MSRC Generator",
          "version": "1.0"
        }
      },
      "id": "msrc_CVE-2026-21537",
      "initial_release_date": "2026-02-10T08:00:00.000Z",
      "revision_history": [
        {
          "date": "2026-02-10T08:00:00.000Z",
          "legacy_version": "1",
          "number": "1",
          "summary": "Information published."
        }
      ],
      "status": "final",
      "version": "1"
    }
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "category": "product_version_range",
            "name": "\u003c1.0.9.0",
            "product": {
              "name": "Microsoft Defender for Endpoint for Linux \u003c1.0.9.0",
              "product_id": "1"
            }
          },
          {
            "category": "product_version",
            "name": "1.0.9.0",
            "product": {
              "name": "Microsoft Defender for Endpoint for Linux 1.0.9.0",
              "product_id": "12015"
            }
          }
        ],
        "category": "product_name",
        "name": "Microsoft Defender for Endpoint for Linux"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-21537",
      "cwe": {
        "id": "CWE-94",
        "name": "Improper Control of Generation of Code (\u0027Code Injection\u0027)"
      },
      "notes": [
        {
          "category": "general",
          "text": "Microsoft",
          "title": "Assigning CNA"
        },
        {
          "category": "faq",
          "text": "An attacker must be an authenticated to a Linux VMs in the same network subnet as the targeted in order to exploit this vulnerability.",
          "title": "According to the CVSS metric, the attack vector is local (AV:A). What does that mean for this vulnerability?"
        },
        {
          "category": "faq",
          "text": "Customers can obtain the fix by ensuring that Microsoft Defender for Endpoint auto\u2011provisioning is enabled in Defender for Cloud; once enabled, all eligible Linux machines will automatically receive MDE extension version 1.0.9.0.\nThe MDE for Linux extension is automatically updated through Azure\u2019s auto\u2011provisioning mechanism. Customers will receive the updated extension (version 1.0.9.0) once auto\u2011provisioning is enabled on the subscription. The backend pushes the newest extension to all onboarded VMs without requiring manual action.\nYou can verify auto\u2011provisioning in Defender for Cloud \u2192 Environment Settings \u2192 Defender Plans \u2192 Servers \u2192 Settings, where the MDE auto\u2011provisioning toggle (WDAgent / MDE extension) is located. Customers can select their subscription and confirm whether the provisioning setting is set to On. Read more here\nEnable auto\u2011provisioning under Defender for Cloud. After it is turned on, all eligible machines in the subscription will automatically receive the updated MDE for Linux extension within up to 6 hours. No further steps are needed.",
          "title": "What action do customers need to take protect themselves from this vulnerability?"
        },
        {
          "category": "faq",
          "text": "An attacker on the same subnet could intercept and respond to the extension\u2019s IMDS request during installation, crafting a malicious JSON response that injects non-sanitized data into a shell command. By doing so, the attacker could cause the installation script to execute arbitrary code as root on the victim\u2019s machine.",
          "title": "How could an attacker exploit this vulnerability?"
        }
      ],
      "product_status": {
        "fixed": [
          "12015"
        ],
        "known_affected": [
          "1"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "CVE-2026-21537 Microsoft Defender for Endpoint Linux Extension Remote Code Execution Vulnerability - HTML",
          "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21537"
        },
        {
          "category": "self",
          "summary": "CVE-2026-21537 Microsoft Defender for Endpoint Linux Extension Remote Code Execution Vulnerability - CSAF",
          "url": "https://msrc.microsoft.com/csaf/advisories/2026/msrc_cve-2026-21537.json"
        }
      ],
      "remediations": [
        {
          "category": "vendor_fix",
          "date": "2026-02-10T08:00:00.000Z",
          "details": "1.0.9.0:Security Update:https://learn.microsoft.com/en-us/azure/defender-for-cloud/integration-defender-for-endpoint?WT.mc_id=Portal-Microsoft_Azure_Security",
          "product_ids": [
            "1"
          ],
          "url": "https://learn.microsoft.com/en-us/azure/defender-for-cloud/integration-defender-for-endpoint?WT.mc_id=Portal-Microsoft_Azure_Security"
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "LOW",
            "attackVector": "ADJACENT_NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "environmentalsScore": 0.0,
            "exploitCodeMaturity": "UNPROVEN",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "remediationLevel": "OFFICIAL_FIX",
            "reportConfidence": "CONFIRMED",
            "scope": "UNCHANGED",
            "temporalScore": 7.7,
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C",
            "version": "3.1"
          },
          "products": [
            "1"
          ]
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Remote Code Execution"
        },
        {
          "category": "exploit_status",
          "details": "Publicly Disclosed:No;Exploited:No;Latest Software Release:Exploitation Less Likely"
        }
      ],
      "title": "Microsoft Defender for Endpoint Linux Extension Remote Code Execution Vulnerability"
    }
  ]
}