CVE-2025-29457
📋 TL;DR
This vulnerability in MyBB 1.8.38 allows remote attackers to obtain sensitive information through the Import a Theme function, potentially via Server-Side Request Forgery (SSRF). The vulnerability affects MyBB forum administrators who have access to the theme import functionality. The vendor disputes the severity, citing administrator permissions and existing SSRF mitigations.
💻 Affected Systems
- MyBB
📦 What is this software?
Mybb by Mybb
⚠️ Risk & Real-World Impact
Worst Case
An attacker could exfiltrate sensitive internal data, access internal services, or perform reconnaissance on internal networks by exploiting SSRF through theme imports.
Likely Case
An authenticated attacker with board administrator privileges could retrieve information from internal systems or services accessible to the MyBB server.
If Mitigated
With proper access controls and network segmentation, impact is limited to information the MyBB server can access, potentially still exposing some internal service metadata.
🎯 Exploit Status
Exploitation requires board administrator credentials. The vulnerability leverages theme import functionality to potentially trigger SSRF.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not available
Vendor Advisory: Not available
Restart Required: No
Instructions:
No official patch available. Monitor MyBB security advisories for updates. Consider implementing workarounds and security controls.
🔧 Temporary Workarounds
Restrict Theme Import Access
allLimit access to the Import a Theme function to only essential administrators and implement additional approval workflows.
Implement Network Controls
allApply network segmentation and firewall rules to restrict MyBB server outbound connections to only necessary external services.
🧯 If You Can't Patch
- Implement strict access controls for board administrator accounts and monitor theme import activities.
- Configure web application firewall (WAF) rules to detect and block suspicious theme import requests.
🔍 How to Verify
Check if Vulnerable:
Check if running MyBB 1.8.38. Review administrator access logs for theme import activities from unexpected sources.Check Version:
Check MyBB Admin CP → Version & Update section or examine inc/config.php for version information.Verify Fix Applied:
Monitor for MyBB security updates. Test theme import functionality with controlled external URLs to verify SSRF protections.📡 Detection & Monitoring
Log Indicators:
- Unusual theme import activities, especially with external URLs in administrator logs
- Multiple failed theme import attempts from same administrator
Network Indicators:
- Outbound connections from MyBB server to internal services following theme imports
- Unusual DNS queries for internal hostnames
SIEM Query:
source="mybb_logs" AND (event="theme_import" OR event="admin_action") AND url CONTAINS "http"