Webserver detection of Log4j RCE (CVE-2021-44228) JNDI injection patterns
Detects webserver traffic containing Log4Shell-style JNDI injection payload strings, excluding Nessus scan artifacts.
- Category
- webserver
- Author
- Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
- Published
- 2021-12-10
- 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 matches webserver requests containing common Log4j JNDI lookup and obfuscation strings associated with the CVE-2021-44228 exploitation attempt. Attackers use these payload patterns to trigger outbound lookups (for example via LDAP/RMI/DNS/others) that can lead to remote code execution. The detection relies on HTTP/webserver telemetry and keyword matches against the request content, while excluding events containing a specific Nessus-related substring.
Reporting behind it
- web.archive.orghttps://web.archive.org/web/20231230220738/https://www.lunasec.io/docs/blog/log4j-zero-day/
- news.ycombinator.comhttps://news.ycombinator.com/item?id=29504755
- github.comhttps://github.com/tangxiaofeng7/apache-log4j-poc
- gist.github.comhttps://gist.github.com/Neo23x0/e4c8b03ff8cdf1fa63b7d15db6e3860b
- github.comhttps://github.com/YfryTchsGD/Log4jAttackSurface
- twitter.comhttps://twitter.com/shutingrz/status/1469255861394866177?s=21
- github.comhttps://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2021/Exploits/CVE-2021-44228/web_cve_2021_44228_log4j.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: Webserver detection of Log4j RCE (CVE-2021-44228) JNDI injection patterns
id: f01064ca-d825-4cdb-9209-98a90f0c2708
status: test
description: This rule matches webserver requests containing common Log4j JNDI lookup and obfuscation strings associated with the CVE-2021-44228 exploitation attempt. Attackers use these payload patterns to trigger outbound lookups (for example via LDAP/RMI/DNS/others) that can lead to remote code execution. The detection relies on HTTP/webserver telemetry and keyword matches against the request content, while excluding events containing a specific Nessus-related substring.
references:
- https://web.archive.org/web/20231230220738/https://www.lunasec.io/docs/blog/log4j-zero-day/
- https://news.ycombinator.com/item?id=29504755
- https://github.com/tangxiaofeng7/apache-log4j-poc
- https://gist.github.com/Neo23x0/e4c8b03ff8cdf1fa63b7d15db6e3860b
- https://github.com/YfryTchsGD/Log4jAttackSurface
- https://twitter.com/shutingrz/status/1469255861394866177?s=21
- https://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2021/Exploits/CVE-2021-44228/web_cve_2021_44228_log4j.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2021-12-10
modified: 2022-02-06
tags:
- attack.initial-access
- attack.t1190
- detection.emerging-threats
logsource:
category: webserver
detection:
keywords:
- ${jndi:ldap:/
- ${jndi:rmi:/
- ${jndi:ldaps:/
- ${jndi:dns:/
- "/$%7bjndi:"
- "%24%7bjndi:"
- "$%7Bjndi:"
- "%2524%257Bjndi"
- "%2F%252524%25257Bjndi%3A"
- "${jndi:${lower:"
- ${::-j}${
- ${jndi:nis
- ${jndi:nds
- ${jndi:corba
- ${jndi:iiop
- "Reference Class Name: foo"
- ${${env:BARFOO:-j}
- ${::-l}${::-d}${::-a}${::-p}
- ${base64:JHtqbmRp
- ${${env:ENV_NAME:-j}ndi${env:ENV_NAME:-:}$
- "${${lower:j}ndi:"
- "${${upper:j}ndi:"
- "${${::-j}${::-n}${::-d}${::-i}:"
filter:
- w.nessus.org/nessus
- /nessus}
condition: keywords and not filter
falsepositives:
- Vulnerability scanning
level: high
license: DRL-1.1
related:
- id: 5ea8faa8-db8b-45be-89b0-151b84c82702
type: derived