Apache Solr CVE-2021-27905 Exploitation Attempt via Web Requests
Alerts when webserver logs show GET requests to Solr endpoints containing CVE-2021-27905-style debug/dump or fetchindex parameters with HTTP 200.
- Category
- webserver
- Author
- @gott_cyber (SigmaHQ), DRL 1.1
- Published
- 2022-12-11
- Updated
- 2026-07-31
ATT&CK techniques
Initial AccessRecon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
What it detects
This rule flags webserver requests consistent with attempts to exploit CVE-2021-27905 against Apache Solr. It matches HTTP responses with status code 200 where the request URI query contains specific Solr debug and fetchindex patterns. The detection relies on webserver HTTP telemetry including request method, URI query, and response status codes.
Reporting behind it
- twitter.comhttps://twitter.com/Al1ex4/status/1382981479727128580
- twitter.comhttps://twitter.com/sec715/status/1373472323538362371
- nsfocusglobal.comhttps://nsfocusglobal.com/apache-solr-arbitrary-file-read-and-ssrf-vulnerability-threat-alert/
- mp.weixin.qq.comhttps://mp.weixin.qq.com/s?__biz=Mzg3NDU2MTg0Ng==&mid=2247484117&idx=1&sn=2fdab8cbe4b873f8dd8abb35d935d186
- github.comhttps://github.com/murataydemir/CVE-2021-27905
- github.comhttps://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2021/Exploits/CVE-2021-27905/web_cve_2021_27905_apache_solr_exploit.yml
Changelog
v5- v5Candidate ingested via manual entry.2026-07-31
- v4Candidate ingested via manual entry.2026-07-31
- v3Candidate ingested via manual entry.2026-07-31
- v2Candidate ingested via manual entry.2026-07-31
- v1No changelog recorded for this version.2026-07-30
Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.
title: Apache Solr CVE-2021-27905 Exploitation Attempt via Web Requests
id: 61c7c1db-ed83-40ca-b0cf-b85646ff1fcf
status: test
description: This rule flags webserver requests consistent with attempts to exploit CVE-2021-27905 against Apache Solr. It matches HTTP responses with status code 200 where the request URI query contains specific Solr debug and fetchindex patterns. The detection relies on webserver HTTP telemetry including request method, URI query, and response status codes.
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
- https://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2021/Exploits/CVE-2021-27905/web_cve_2021_27905_apache_solr_exploit.yml
author: "@gott_cyber, Huntrule Team"
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
license: DRL-1.1
related:
- id: 0bbcd74b-0596-41a4-94a0-4e88a76ffdb3
type: derived