CVE-2023-27755
📋 TL;DR
CVE-2023-27755 is an arbitrary file download vulnerability in go-bbs v1 that allows attackers to download any file from the server via the /api/v1/download endpoint. This affects all users running go-bbs v1 without proper access controls. Attackers can potentially access sensitive system files and configuration data.
💻 Affected Systems
- go-bbs
📦 What is this software?
Go Bbs by 71note
⚠️ Risk & Real-World Impact
Worst Case
Complete server compromise through downloading sensitive files like SSH keys, configuration files with credentials, or database backups leading to data exfiltration and lateral movement.
Likely Case
Unauthorized access to sensitive application files, configuration data, and potentially user data stored in accessible directories.
If Mitigated
Limited impact with proper file system permissions and network segmentation preventing access to critical system files.
🎯 Exploit Status
Simple HTTP request to /api/v1/download with file path parameter can exploit this vulnerability.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v1.0.1 or later
Vendor Advisory: https://github.com/gobbscom/go-bbs/issues/10
Restart Required: Yes
Instructions:
1. Update go-bbs to version v1.0.1 or later. 2. Restart the go-bbs service. 3. Verify the fix by testing the /api/v1/download endpoint.
🔧 Temporary Workarounds
Web Server Access Control
allImplement access controls at web server level to restrict access to /api/v1/download endpoint
# Example nginx configuration
location /api/v1/download {
deny all;
}
File System Permissions
linuxRestrict file system permissions to limit accessible directories
chmod 750 /var/www/go-bbs
chown -R www-data:www-data /var/www/go-bbs
🧯 If You Can't Patch
- Implement strict network segmentation to isolate go-bbs from sensitive systems
- Deploy WAF rules to block requests to /api/v1/download with suspicious file paths
🔍 How to Verify
Check if Vulnerable:
Test if /api/v1/download endpoint accepts arbitrary file paths by attempting to download a known file like /etc/passwd (Linux) or C:\Windows\win.ini (Windows)Check Version:
go-bbs --version or check package manager for installed versionVerify Fix Applied:
After patching, test the same exploit attempt should return an error or be blocked📡 Detection & Monitoring
Log Indicators:
- Multiple requests to /api/v1/download with unusual file paths
- Access to sensitive file paths in download logs
Network Indicators:
- Unusual traffic patterns to /api/v1/download endpoint
- Large file downloads from unexpected sources
SIEM Query:
source="go-bbs" AND uri="/api/v1/download" AND (filepath="*../*" OR filepath="*/etc/*" OR filepath="*/windows/*")