Kaseya VSA < 9.5.7 - Credential Disclosure via Windows Agent

Exploited in the wild. Listed by CISA on 2021-11-03; known to be used by ransomware.

criticalseverity

10CVSS score

85.7%likelihood of exploitation, next 30 days

100%of all CVEs are less likely

Readycheck to confirm it

Kaseya VSA before 9.5.7 allows credential disclosure, as exploited in the wild in July 2021. By default Kaseya VSA on premise offers a download page where the clients for the installation can be downloaded. The default URL for this page is https://x.x.x.x/dl.asp When an attacker download a client for Windows and installs it, the file KaseyaD.ini is generated (C:\Program Files (x86)\Kaseya\XXXXXXXXXX\KaseyaD.ini) which contains an Agent_Guid and AgentPassword This Agent_Guid and AgentPassword can be used to log in on dl.asp (https://x.x.x.x/dl.asp?un=840997037507813&pw=113cc622839a4077a84837485ced6b93e440bf66d44057713cb2f95e503a06d9) This request authenticates the client and returns a sessionId cookie that can be used in subsequent attacks to bypass authentication. Security issues discovered --- * Unauthenticated download page leaks credentials * Credentials of agent software can be used to obtain a sessionId (cookie) that can be used for services not intended for use by agents * dl.asp accepts credentials via a GET request * Access to KaseyaD.ini gives an attacker access to sufficient information to penetrate the Kaseya installation and its clients. Impact --- Via the page /dl.asp enough information can be obtained to give an attacker a sessionId that can be used to execute further (semi-authenticated) attacks against the system.

Impact

Unauthenticated attackers can obtain Agent_Guid and AgentPassword credentials via the download page, gaining authenticated access to execute further attacks against Kaseya VSA.

Fix

Update to version 9.5.7 or later to remediate this vulnerability.

How to confirm it

Send: GET {{BaseURL}}/dl.asp
Positive when: contains_all(body, '<title>Download Agent</title>', 'mkDefault.asp?id=') and status_code == 200
Send: GET {{BaseURL}}/mkDefault.asp?id={{mkdefault_id}}
Positive when: matches in header /Location: /install/VSA-default-([0-9-]+)/KcsSetup\.exe/ AND status 302

Run it with nuclei: nuclei -id CVE-2021-30116 -u <target>

The full check

id: CVE-2021-30116

info:
  name: Kaseya VSA < 9.5.7 - Credential Disclosure via Windows Agent
  author: daffainfo
  severity: critical
  description: |
    Kaseya VSA before 9.5.7 allows credential disclosure, as exploited in the wild in July 2021. By default Kaseya VSA on premise offers a download page where the clients for the installation can be downloaded. The default URL for this page is https://x.x.x.x/dl.asp When an attacker download a client for Windows and installs it, the file KaseyaD.ini is generated (C:\Program Files (x86)\Kaseya\XXXXXXXXXX\KaseyaD.ini) which contains an Agent_Guid and AgentPassword This Agent_Guid and AgentPassword can be used to log in on dl.asp (https://x.x.x.x/dl.asp?un=840997037507813&pw=113cc622839a4077a84837485ced6b93e440bf66d44057713cb2f95e503a06d9) This request authenticates the client and returns a sessionId cookie that can be used in subsequent attacks to bypass authentication. Security issues discovered --- * Unauthenticated download page leaks credentials * Credentials of agent software can be used to obtain a sessionId (cookie) that can be used for services not intended for use by agents * dl.asp accepts credentials via a GET request * Access to KaseyaD.ini gives an attacker access to sufficient information to penetrate the Kaseya installation and its clients. Impact --- Via the page /dl.asp enough information can be obtained to give an attacker a sessionId that can be used to execute further (semi-authenticated) attacks against the system.
  impact: |
    Unauthenticated attackers can obtain Agent_Guid and AgentPassword credentials via the download page, gaining authenticated access to execute further attacks against Kaseya VSA.
  remediation: |
    Update to version 9.5.7 or later to remediate this vulnerability.
  reference:
    - https://csirt.divd.nl/2021/07/04/Kaseya-Case-Update-2/
    - https://csirt.divd.nl/2021/07/07/Kaseya-Limited-Disclosure/
    - https://helpdesk.kaseya.com/hc/en-gb/articles/4403440684689-Important-Notice-July-2nd-2021
    - https://www.secpod.com/blog/kaseya-vsa-zero-day-by-revil/
    - https://nvd.nist.gov/vuln/detail/CVE-2021-30116
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
    cvss-score: 10.0
    cve-id: CVE-2021-30116
    epss-score: 0.85735
    epss-percentile: 0.99728
    cwe-id: CWE-522
    cpe: cpe:2.3:a:kaseya:virtual_system_administrator:*:*:*:*:*:*:*:*
  metadata:
    verified: true
    vendor: kaseya
    product: virtual_system_administrator
    shodan-query: http.favicon.hash:-1445519482
  tags: cve,cve2021,kaseya,virtual_system_administrator,kev,vkev,vuln

flow: |
  http(1)
  for (let mkdefault_id of iterate(template.id)) {
    set("mkdefault_id", mkdefault_id)
    http(2)
  }

http:
  - method: GET
    path:
      - "{{BaseURL}}/dl.asp"

    matchers:
      - type: dsl
        dsl:
          - "contains_all(body, '<title>Download Agent</title>', 'mkDefault.asp?id=')"
          - "status_code == 200"
        condition: and
        internal: true

    extractors:
      - type: regex
        name: id
        group: 1
        internal: true
        regex:
          - 'mkDefault\.asp\?id=([0-9-]+)'

  - method: GET
    path:
      - "{{BaseURL}}/mkDefault.asp?id={{mkdefault_id}}"

    matchers-condition: and
    matchers:
      - type: regex
        part: header
        regex:
          - "Location: /install/VSA-default-([0-9-]+)/KcsSetup\\.exe"

      - type: status
        status:
          - 302

References

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