CVE-2025-56223
📋 TL;DR
CVE-2025-56223 is a denial-of-service vulnerability in SigningHub v8.6.8 where attackers can upload excessive files to the /Home/UploadStreamDocument endpoint due to missing rate limiting. This affects organizations using vulnerable SigningHub installations, potentially disrupting document signing services.
💻 Affected Systems
- SigningHub
📦 What is this software?
Signinghub by Ascertia
⚠️ Risk & Real-World Impact
Worst Case
Complete service unavailability for SigningHub, preventing all document signing operations and potentially affecting business continuity.
Likely Case
Temporary service degradation or downtime for the SigningHub application, disrupting document workflows.
If Mitigated
Minimal impact with proper rate limiting and monitoring in place.
🎯 Exploit Status
The GitHub reference contains exploit details. Attack requires only HTTP access to the vulnerable endpoint with no authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: http://ascertia.com
Restart Required: No
Instructions:
Check Ascertia/SigningHub vendor advisory for official patch. Upgrade to fixed version when available.
🔧 Temporary Workarounds
Implement Web Application Firewall (WAF) Rules
allConfigure WAF to rate limit requests to /Home/UploadStreamDocument endpoint
WAF-specific configuration commands vary by vendor
Network Access Control
linuxRestrict access to SigningHub endpoints to trusted IP ranges only
iptables -A INPUT -p tcp --dport <port> -s <trusted_ip> -j ACCEPT
iptables -A INPUT -p tcp --dport <port> -j DROP
🧯 If You Can't Patch
- Implement rate limiting at reverse proxy/load balancer level
- Monitor for abnormal upload patterns and implement alerting
🔍 How to Verify
Check if Vulnerable:
Test if /Home/UploadStreamDocument endpoint accepts multiple rapid file uploads without throttlingCheck Version:
Check SigningHub admin interface or configuration files for version informationVerify Fix Applied:
Verify rate limiting is enforced on the endpoint after implementing controls📡 Detection & Monitoring
Log Indicators:
- High frequency of POST requests to /Home/UploadStreamDocument
- Unusual upload patterns from single IP addresses
Network Indicators:
- Spike in traffic to SigningHub upload endpoint
- Multiple large file uploads in short timeframes
SIEM Query:
source="signinghub" AND uri_path="/Home/UploadStreamDocument" | stats count by src_ip | where count > 100