CVE-2019-11574
📋 TL;DR
CVE-2019-11574 is a Server-Side Request Forgery (SSRF) vulnerability in Simple Machines Forum (SMF) that allows attackers to make unauthorized HTTP requests from the vulnerable server. This can lead to internal network scanning, data exfiltration, or attacks against internal services. All SMF installations before version 2.0.17 are affected.
💻 Affected Systems
- Simple Machines Forum (SMF)
📦 What is this software?
Simple Machine Forum by Simplemachines
⚠️ Risk & Real-World Impact
Worst Case
Attackers could pivot to internal networks, access sensitive internal services, perform port scanning, or execute attacks against backend systems that trust the SMF server.
Likely Case
Information disclosure from internal services, scanning of internal network segments, or limited data exfiltration from services accessible to the SMF server.
If Mitigated
Limited impact if network segmentation restricts SMF server's access to internal resources and external requests are filtered.
🎯 Exploit Status
Exploitation requires some level of user access, but the vulnerability is in core functionality and has public proof-of-concept available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.0.17 and later
Vendor Advisory: https://www.simplemachines.org/community/index.php?topic=558175.0
Restart Required: No
Instructions:
1. Backup your SMF installation and database. 2. Download SMF 2.0.17 or later from the official website. 3. Replace all files with the new version, preserving your configuration files. 4. Run the upgrade script if upgrading from older versions.
🔧 Temporary Workarounds
Input Validation for URL Parameters
allAdd validation to reject URLs pointing to internal IP ranges or localhost
Modify Subs-Package.php and Subs.php to validate URLs before curl execution
Network Restriction
allRestrict outbound network access from SMF server to only necessary external services
Configure firewall rules to block SMF server from accessing internal network ranges
🧯 If You Can't Patch
- Implement strict network segmentation to isolate SMF server from internal resources
- Deploy a web application firewall (WAF) with SSRF protection rules
🔍 How to Verify
Check if Vulnerable:
Check SMF version in admin panel or examine Subs-Package.php and Subs.php files for unvalidated curl callsCheck Version:
Check SMF version in admin panel or examine Settings.php for version informationVerify Fix Applied:
Verify SMF version is 2.0.17 or later and test that URL parameters are properly validated📡 Detection & Monitoring
Log Indicators:
- Unusual curl requests from SMF server to internal IPs
- HTTP requests to unexpected domains or IP ranges
Network Indicators:
- SMF server making requests to internal network segments
- Outbound connections to unusual ports from SMF server
SIEM Query:
source="smf-logs" AND (url_contains="localhost" OR url_contains="127.0.0.1" OR url_contains="192.168" OR url_contains="10." OR url_contains="172.16")