CVE-2025-54320
📋 TL;DR
Ascertia SigningHub versions through 8.6.8 have an email bombing vulnerability in the invite user function due to lack of rate limiting. Authenticated attackers can automate invite requests to flood target email addresses. This affects all Ascertia SigningHub deployments up to version 8.6.8.
💻 Affected Systems
- Ascertia SigningHub
📦 What is this software?
Signinghub by Ascertia
⚠️ Risk & Real-World Impact
Worst Case
Email servers become overwhelmed, causing service disruption, potential email blacklisting, and denial of service for legitimate users.
Likely Case
Targeted email bombing causing inbox flooding, potential email service disruption, and reputational damage to the organization.
If Mitigated
Minimal impact with proper rate limiting and monitoring in place.
🎯 Exploit Status
Exploitation requires authenticated access. Public proof-of-concept available on GitHub.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 8.6.9 or later
Vendor Advisory: https://www.ascertia.com/company/vulnerability-disclosure-policy/
Restart Required: Yes
Instructions:
1. Download latest version from Ascertia support portal. 2. Backup current installation. 3. Apply patch/upgrade to 8.6.9+. 4. Restart SigningHub services. 5. Verify functionality.
🔧 Temporary Workarounds
Implement Web Application Firewall (WAF) Rules
allAdd rate limiting rules for invite endpoint requests
# WAF-specific configuration required
Modify Application Configuration
allImplement custom rate limiting in application layer
# Application-specific configuration required
🧯 If You Can't Patch
- Implement network-level rate limiting for SigningHub invite endpoints
- Monitor and alert on unusual invite request patterns
🔍 How to Verify
Check if Vulnerable:
Check SigningHub version in admin panel. If version is 8.6.8 or earlier, system is vulnerable.Check Version:
# Check version via admin interface or application logsVerify Fix Applied:
Verify version is 8.6.9 or later in admin panel. Test invite functionality with rate limiting.📡 Detection & Monitoring
Log Indicators:
- High frequency of invite requests from single user
- Multiple failed invite attempts
- Unusual invite patterns outside business hours
Network Indicators:
- Spike in POST requests to invite endpoints
- Abnormal email traffic from SigningHub server
SIEM Query:
source="signinghub" AND (event="user_invite" OR endpoint="/invite") | stats count by user, src_ip | where count > threshold