{
  "id": "CVE-2026-55040",
  "url": "https://spydr.io/cve/CVE-2026-55040",
  "published": "2026-07-14T18:18:15.413Z",
  "modified": "2026-08-19T04:17:23.540Z",
  "score": 9.1,
  "severity": "critical",
  "cvss_version": "3.1",
  "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
  "score_source": "microsoft.com",
  "epss": 0.69536,
  "epss_percentile": 0.99347,
  "exploited": true,
  "kev": {
    "added": "2026-08-18",
    "due": "2026-08-21",
    "action": "Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.",
    "ransomware": "Unknown",
    "name": "Microsoft SharePoint Weak Authentication Vulnerability",
    "notes": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-55040"
  },
  "ssvc_exploitation": "active",
  "vendors": [
    "Microsoft"
  ],
  "products": [
    "Microsoft SharePoint Enterprise Server 2016",
    "Microsoft SharePoint Server 2019",
    "Microsoft SharePoint Server Subscription Edition"
  ],
  "cwes": [
    "CWE-1390"
  ],
  "description": "Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.",
  "status": "Analyzed",
  "score_type": "Secondary",
  "scores": {
    "cvss_v40": null,
    "cvss_v31": 9.1,
    "cvss_v30": null
  },
  "references": [
    {
      "url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ]
    },
    {
      "url": "https://github.com/sfewer-r7/CVE-2026-55040",
      "tags": [
        "Exploit"
      ]
    },
    {
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-55040",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ]
    },
    {
      "url": "https://www.rapid7.com/blog/post/ra-microsoft-sharepoint-jwt-token-authentication-bypass-cve-2026-55040/",
      "tags": [
        "US Government Resource"
      ]
    }
  ],
  "nvd_url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55040",
  "covered_in": [],
  "attribution": [
    {
      "source": "NVD",
      "url": "https://nvd.nist.gov",
      "notice": "This product uses data from the NVD API but is not endorsed or certified by the NVD."
    },
    {
      "source": "CISA KEV",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "notice": "Known exploited vulnerabilities from the CISA KEV catalog."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss",
      "notice": "Exploit prediction scores from FIRST EPSS."
    }
  ]
}