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WAFv2 web ACL does not include the 'AWSManagedRulesKnownBadInputsRuleSet' managed rule group Affecting WAF service in AWS

Severity

0.0
high
0
10
    Severity Framework
    Snyk CCSS
    Rule category
    Network / Firewall

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  • Snyk ID SNYK-CC-00185
  • credit Snyk Research Team
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Description

The 'Known bad inputs' (AWSManagedRulesKnownBadInputsRuleSet) managed rule group contains rules that block request patterns that are invalid or known to be associated with vulnerabilities, such as Log4j.

How to fix?

Set rule.statement.managed_rule_group_statement.name to AWSManagedRulesKnownBadInputsRuleSet and rule.statement.managed_rule_group_statement.vendor_name to AWS.

Additionally, rule.override_action must not be set to count, and the following rules must not be excluded:

  • Log4JRCE
  • Log4JRCE_ALL_HEADER

Note that the 'Log4JRCE' WAFv2 rule (and many others) only inspects the first 8 KB of the request body, so you may additionally want to ensure that the 'Core rule set' (AWSManagedRulesCommonRuleSet) is also included, as the 'SizeRestrictions_BODY' rule in that managed rule group verifies that the request body size is at most 8 KB.

Example Configuration

resource "aws_wafv2_web_acl" "valid1" {
  name        = "valid1"
  scope       = "CLOUDFRONT"

  default_action {
    allow {}
  }

  rule {
    name     = "valid1rule1"
    priority = 1

    override_action {
      none {}
    }

    statement {
      managed_rule_group_statement {
        name        = "AWSManagedRulesKnownBadInputsRuleSet"
        vendor_name = "AWS"
      }
    }

    visibility_config {
      cloudwatch_metrics_enabled = false
      metric_name                = "friendly-rule-metric-name"
      sampled_requests_enabled   = false
    }
  }

  visibility_config {
    cloudwatch_metrics_enabled = false
    metric_name                = "friendly-metric-name"
    sampled_requests_enabled   = false
  }
}