EXPL_Log4j_CVE_2021_44228_Dec21_Hard

YARA detection rule by Florian Roth · NOASSERTION

Detects indicators in server logs that indicate the exploitation of CVE-2021-44228

rule EXPL_Log4j_CVE_2021_44228_Dec21_Hard {
   meta:
      description = "Detects indicators in server logs that indicate the exploitation of CVE-2021-44228"
      author = "Florian Roth"
      reference = "https://twitter.com/h113sdx/status/1469010902183661568?s=20"
      date = "2021-12-10"
      score = 80
   strings:
      $x1 = /\$\{jndi:(ldap|ldaps|rmi|dns):\/[\/]?[a-z-\.0-9]{3,120}:[0-9]{2,5}\/[a-zA-Z\.]{1,32}\}/
      $fp1r = /(ldap|rmi|ldaps|dns):\/[\/]?(127\.0\.0\.1|192\.168\.|172\.[1-3][0-9]\.|10\.)/
   condition:
      $x1 and not 1 of ($fp*)
}

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

618cc859-0038-418c-931e-787d47310ad4

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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