NGINX Servers Targeted in Traffic-Hijacking Cyberattack Campaign

NGINX Servers Exploited to Redirect User Traffic in Ongoing Cyberattack

Security researchers have identified an active campaign in which threat actors compromise NGINX servers to hijack and redirect user traffic through attacker-controlled infrastructure. The operation, which remains under investigation, poses significant risks for data interception, credential theft, and secondary malware distribution.

Attack Overview

The campaign targets vulnerable or misconfigured NGINX servers, a widely used web server and reverse proxy platform. Once compromised, attackers modify server configurations to redirect legitimate traffic to malicious endpoints. This technique enables adversaries to intercept sensitive data, inject malicious payloads, or conduct man-in-the-middle (MITM) attacks against unsuspecting users.

While specific exploitation methods remain undisclosed, common attack vectors for NGINX compromises include:

• Exposed administrative interfaces (e.g., default credentials, weak authentication)
• Outdated software versions with unpatched vulnerabilities
• Misconfigured reverse proxy rules allowing unauthorized access
• Supply chain attacks via compromised third-party modules

Technical Impact Analysis

The traffic redirection mechanism operates at the server level, making detection challenging for end-users. Key risks include:

1. Data Exposure: Intercepted traffic may contain sensitive information such as:

   • Authentication credentials
   • Session cookies
   • Payment card data (if processing occurs on affected servers)
   • Proprietary business communications

2. Secondary Exploitation: Redirected users may be exposed to:

   • Malware downloads (e.g., infostealers, ransomware)
   • Phishing landing pages
   • Cryptojacking scripts

3. Reputation Damage: Organizations may face:

   • Loss of customer trust
   • Compliance violations (e.g., GDPR, PCI DSS)
   • Brand degradation from malicious redirects

Detection and Mitigation Recommendations

Security teams should prioritize the following actions:

Immediate Response

• Audit NGINX configurations for unauthorized modifications, particularly in:
  • nginx.conf and included configuration files
  • Reverse proxy rules (proxy_pass directives)
  • Server block (server {}) definitions
• Review network traffic for unexpected outbound connections to unfamiliar IP addresses or domains
• Rotate credentials for all NGINX-related services, including:
  • Administrative interfaces
  • Database connections
  • API keys

Long-Term Hardening

• Update NGINX to the latest stable version, addressing known vulnerabilities (e.g., CVE-2022-41741, CVE-2021-23017)
• Implement least-privilege access for NGINX processes and administrators
• Deploy file integrity monitoring (FIM) to detect unauthorized configuration changes
• Enable logging and monitoring for:
  • Configuration file modifications
  • Unusual traffic patterns (e.g., spikes in redirects)
  • Failed authentication attempts
• Segment NGINX servers from critical internal networks to limit lateral movement potential

User-Side Protections

• Educate users to recognize signs of traffic hijacking, such as:
  • Unexpected SSL/TLS certificate warnings
  • Unfamiliar domain redirects
  • Slow or unusual browsing behavior
• Enforce HTTPS with HSTS (HTTP Strict Transport Security) to mitigate MITM risks

Industry Context

NGINX powers over 30% of global web servers, making it a high-value target for threat actors. Similar campaigns have historically exploited:

• CVE-2019-20372: NGINX resolver vulnerability enabling cache poisoning
• CVE-2017-7529: Integer overflow in NGINX range filter module

Organizations are advised to treat NGINX servers as critical assets requiring continuous monitoring and proactive hardening. Further details on attack methodologies are expected as investigations progress.