ModSecurity CRS RuleID-960911

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Rule ID: 906911

Rule Message: Invalid HTTP Request Line


SecRule REQUEST_LINE "!^(?:(?:[a-z]{3,10}\s+(?:\w{3,7}?://[\w\-\./]*(?::\d+)?)?/[^?#]*(?:\?[^#\s]*)?(?:#[\S]*)?|connect (?:\d{1,3}\.){3}\d{1,3}\.?(?::\d+)?|options \*)\s+[\w\./]+|get /[^?#]*(?:\?[^#\s]*)?(?:#[\S]*)?)$" \
"t:none,t:lowercase,phase:2,rev:'2.0.8',pass,nolog,auditlog,msg:'Invalid HTTP Request Line',id:'960911',severity:'4',tag:'',setvar:'tx.msg=%{rule.msg}',setvar:tx.anomaly_score=+%{tx.notice_anomaly_score},setvar:tx.protocol_violation_score=+%{tx.notice_anomaly_score},setvar:'tx.%{}-PROTOCOL_VIOLATION/INVALID_REQ-%{matched_var_name}=%{matched_var}'"

Rule Summary

  • Validate request line against the format specified in the HTTP RFC
  • Uses rule negation against the regex for positive security. The regex specifies the proper construction of URI request lines such as:
"http:" "//" host [ ":" port ] [ abs_path [ "?" query ]] 
  • It also outlines proper construction for CONNECT, OPTIONS and GET requests.


4- Warning.

Detailed Information

Provide detailed information about the rule construction such as:

  • Why the variable list specified was used
  • A description of the regular expression used - what is is looking for in plain english
  • What actions are used and why

Affected Software

If this attack only affects a specific piece of public software (if this is a virtual patch for a public disclosure) specify which info.

Attack Scenarios

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Ease of Attack

How easy is it for an attacker to carry out the attack?

Ease of Detection

How easy is it for a defender to use ModSecurity to accurately detect this attack?

False Positives

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False Negatives

Are there any know issues with evasions or how an attacker might bypass detection?

Corrective Action

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Additional References

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