EXPL_Log4j_CVE_2021_44228_JAVA_Exception_Dec21_1

YARA detection rule by Florian Roth · NOASSERTION

Detects exceptions found in server logs that indicate an exploitation attempt of CVE-2021-44228

rule EXPL_Log4j_CVE_2021_44228_JAVA_Exception_Dec21_1 {
   meta:
      description = "Detects exceptions found in server logs that indicate an exploitation attempt of CVE-2021-44228"
      author = "Florian Roth"
      reference = "https://gist.github.com/Neo23x0/e4c8b03ff8cdf1fa63b7d15db6e3860b"
      date = "2021-12-12"
      score = 60
   strings:
      $xa1 = "header with value of BadAttributeValueException: "

      $sa1 = ".log4j.core.net.JndiManager.lookup(JndiManager"
      $sa2 = "Error looking up JNDI resource"
   condition:
      $xa1 or all of ($sa*)
}

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

f517384b-70a1-48ea-8d0c-827c7db81ade

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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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What do these messages mean?

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

[[ currentRule.title ]]

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