CVE-2026-42285: Critical GoBGP Flaw Allows Remote Crash via Malformed UPDATE

title: CVE-2026-42285: GoBGP Malformed UPDATE causing Nil Pointer Dereference
id: scw-2026-05-07-ai-1
status: experimental
level: critical
description: |
  This rule detects potential exploitation attempts targeting CVE-2026-42285. It looks for network traffic directed to the BGP port (179) from any source IP. The vulnerability allows an unauthenticated remote BGP peer to trigger a denial-of-service by sending a malformed BGP UPDATE message, causing GoBGP to crash. While this rule specifically targets the network vector (port 179), a more precise detection would require analyzing the BGP UPDATE message content for inconsistent attribute lengths, which is not directly supported by the provided log source categories and fields. This rule serves as a high-level indicator for potential exploitation attempts on the BGP service.
author: SCW Feed Engine (AI-generated)
date: 2026-05-07
references:
  - https://shimiscyberworld.com/posts/nvd-CVE-2026-42285/
tags:
  - attack.initial_access
  - attack.t1190
logsource:
    category: firewall
detection:
  selection:
      dst_port:
          - '179'
      src_ip:
          - '0.0.0.0/0'
      dst_ip:
          - '0.0.0.0/0'
  selection_indicators:
      # This is a placeholder for a specific malformed BGP UPDATE message pattern.
      # In a real-world scenario, you would need to analyze network traffic
      # or exploit details to identify specific byte sequences or attribute length anomalies.
      # For demonstration, we'll use a hypothetical indicator.
      # Example: Detecting a specific sequence that might indicate inconsistent attribute lengths.
      # This would require deep packet inspection capabilities and specific signatures.
      # For a firewall log, this might be a custom payload signature if supported.
      # If firewall logs do not support deep packet inspection for BGP attributes, this rule might be less effective.
      # A more realistic approach might involve IDS/IPS logs if available and integrated.
      # Assuming a hypothetical field 'bgp_update_payload' for demonstration:
      # bgp_update_payload|contains:
      #     - 'SPECIFIC_MALFORMED_UPDATE_PATTERN'
      # Since we are limited to the provided fields, and BGP traffic is typically on port 179,
      # we will focus on the port and assume that if a crash occurs, it's due to a malformed packet.
      # Without specific payload indicators in the provided fields, this rule is indicative.
      # A more robust detection would require network traffic analysis tools.
      # For the purpose of this exercise, we'll assume that any BGP traffic (port 179) from an unauthenticated peer
      # that leads to a crash (which is not directly logged by firewall but inferred from system logs)
      # is a potential indicator. This rule is therefore a baseline.
      # A more specific rule would require access to BGP-level logs or IDS/IPS signatures.
      # Given the constraints, we focus on the network vector to the BGP port.
      # The actual detection of the malformed packet requires more specific log sources/fields.
      # This rule is a proxy for detecting potential exploitation attempts on the BGP port.
      # A more accurate rule would need to inspect the BGP UPDATE message content.
      # For now, we'll use a broad indicator on port 179, assuming subsequent system logs would confirm the crash.
      # If 'action' field is available and logs successful connection attempts to port 179:
      action|contains:
          - 'ALLOW'
  condition: selection AND selection_indicators
falsepositives:
  - Legitimate administrative activity

Source: Shimi's Cyber World · License & reuse