CVE-2019-17669
📋 TL;DR
WordPress before version 5.2.4 contains a Server-Side Request Forgery (SSRF) vulnerability in URL validation that allows hex character interpretation bypass. This enables attackers to make unauthorized internal network requests from the WordPress server. All WordPress sites running affected versions are vulnerable.
💻 Affected Systems
- WordPress
📦 What is this software?
Wordpress by Wordpress
⚠️ Risk & Real-World Impact
Worst Case
Attackers can access internal services, exfiltrate sensitive data, perform port scanning, or pivot to attack internal systems behind firewalls.
Likely Case
Information disclosure from internal services, reconnaissance of internal network, or abuse of internal APIs.
If Mitigated
Limited impact if network segmentation restricts internal service access and proper egress filtering is in place.
🎯 Exploit Status
Exploitation requires finding WordPress functionality that uses the vulnerable URL validation function. Multiple attack vectors exist through plugins/themes using wp_remote_get() or similar functions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: WordPress 5.2.4
Vendor Advisory: https://wordpress.org/news/2019/10/wordpress-5-2-4-security-release/
Restart Required: No
Instructions:
1. Backup your WordPress site. 2. Update WordPress to version 5.2.4 or later via Dashboard > Updates. 3. Verify update completed successfully. 4. Update all plugins and themes.
🔧 Temporary Workarounds
Restrict HTTP requests
allBlock outgoing HTTP requests from WordPress to internal IP ranges
Add to wp-config.php: define('WP_HTTP_BLOCK_EXTERNAL', true);
Add to wp-config.php: define('WP_ACCESSIBLE_HOSTS', 'example.com,*.wordpress.org');
🧯 If You Can't Patch
- Implement network segmentation to restrict WordPress server access to internal services
- Deploy web application firewall (WAF) with SSRF protection rules
🔍 How to Verify
Check if Vulnerable:
Check WordPress version in Dashboard > Updates or via wp-admin/about.php. Also check source code for wp_http_validate_url() usage patterns.Check Version:
wp core version (WP-CLI) or check wp-includes/version.phpVerify Fix Applied:
Verify WordPress version is 5.2.4 or later. Check that hex-encoded URLs are properly rejected by the validation function.📡 Detection & Monitoring
Log Indicators:
- Unusual outbound HTTP requests from WordPress server to internal IPs
- Requests containing hex-encoded characters in URLs
- Multiple failed validation attempts
Network Indicators:
- WordPress server making requests to internal services
- HTTP traffic to unusual internal ports from web server
SIEM Query:
source="wordpress" AND (url="*%*" OR dest_ip=10.* OR dest_ip=172.16.* OR dest_ip=192.168.*)🔗 References
- https://blog.wpscan.org/wordpress/security/release/2019/10/15/wordpress-524-security-release-breakdown.html
- https://core.trac.wordpress.org/changeset/46475
- https://github.com/WordPress/WordPress/commit/608d39faed63ea212b6c6cdf9fe2bef92e2120ea
- https://lists.debian.org/debian-lts-announce/2019/11/msg00000.html
- https://seclists.org/bugtraq/2020/Jan/8
- https://wordpress.org/news/2019/10/wordpress-5-2-4-security-release/
- https://wpvulndb.com/vulnerabilities/9912
- https://www.debian.org/security/2020/dsa-4599
- https://www.debian.org/security/2020/dsa-4677
- https://blog.wpscan.org/wordpress/security/release/2019/10/15/wordpress-524-security-release-breakdown.html
- https://core.trac.wordpress.org/changeset/46475
- https://github.com/WordPress/WordPress/commit/608d39faed63ea212b6c6cdf9fe2bef92e2120ea
- https://lists.debian.org/debian-lts-announce/2019/11/msg00000.html
- https://seclists.org/bugtraq/2020/Jan/8
- https://wordpress.org/news/2019/10/wordpress-5-2-4-security-release/
- https://wpvulndb.com/vulnerabilities/9912
- https://www.debian.org/security/2020/dsa-4599
- https://www.debian.org/security/2020/dsa-4677
