Detection rules › Sigma

Potential CVE-2021-27905 Exploitation Attempt

Status
test
Severity
medium
Log source
category webserver
Author
@gott_cyber
Source
github.com/SigmaHQ/sigma

Detects exploitation attempt of the CVE-2021-27905 which affects all Apache Solr versions prior to and including 8.8.1.

Known false positives

  • Vulnerability Scanners

MITRE ATT&CK coverage

TacticTechniques
Initial Access

Rule body

title: Potential CVE-2021-27905 Exploitation Attempt
id: 0bbcd74b-0596-41a4-94a0-4e88a76ffdb3
status: test
description: Detects exploitation attempt of the CVE-2021-27905 which affects all Apache Solr versions prior to and including 8.8.1.
references:
    - https://twitter.com/Al1ex4/status/1382981479727128580
    - https://twitter.com/sec715/status/1373472323538362371
    - https://nsfocusglobal.com/apache-solr-arbitrary-file-read-and-ssrf-vulnerability-threat-alert/
    - https://mp.weixin.qq.com/s?__biz=Mzg3NDU2MTg0Ng==&mid=2247484117&idx=1&sn=2fdab8cbe4b873f8dd8abb35d935d186
    - https://github.com/murataydemir/CVE-2021-27905
author: '@gott_cyber'
date: 2022-12-11
modified: 2023-03-24
tags:
    - attack.initial-access
    - attack.t1190
    - cve.2021-27905
    - detection.emerging-threats
logsource:
    category: webserver
detection:
    selection_request1:
        cs-uri-query|contains|all:
            - '/solr/'
            - '/debug/dump?'
            - 'param=ContentStream'
        sc-status: 200
    selection_request2:
        cs-method: 'GET'
        cs-uri-query|contains|all:
            - '/solr/'
            - 'command=fetchindex'
            - 'masterUrl='
        sc-status: 200
    condition: 1 of selection_*
falsepositives:
    - Vulnerability Scanners
level: medium

Stages and Predicates

Stage 0: condition

1 of selection_*

Stage 1: selection_request1

selection_request1:
    cs-uri-query|contains|all:
        - '/solr/'
        - '/debug/dump?'
        - 'param=ContentStream'
    sc-status: 200

Stage 2: selection_request2

selection_request2:
    cs-method: 'GET'
    cs-uri-query|contains|all:
        - '/solr/'
        - 'command=fetchindex'
        - 'masterUrl='
    sc-status: 200

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
cs-methodeq
  • GET
field:"cs-method" kind:eq value:"GET"
cs-uri-querymatch
  • /debug/dump?
  • /solr/
  • command=fetchindex
  • masterUrl=
  • param=ContentStream
field:"cs-uri-query" kind:match
sc-statuseq
  • 200
field:"sc-status" kind:eq value:"200"