CVE-2025-58436
📋 TL;DR
CVE-2025-58436 is a denial-of-service vulnerability in OpenPrinting CUPS where an attacker can send slow messages to the cupsd service, causing it to become unresponsive to legitimate clients. This affects all systems running CUPS versions prior to 2.4.15. The vulnerability allows resource exhaustion through slow message transmission.
💻 Affected Systems
- OpenPrinting CUPS
📦 What is this software?
Cups by Openprinting
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of printing services across the entire system, potentially affecting all users and applications that rely on CUPS for printing functionality.
Likely Case
Temporary disruption of printing services for legitimate users while the slow message attack is ongoing, with service restoration after the attack stops.
If Mitigated
Minimal impact with proper network segmentation and monitoring; printing services remain available to internal users while external attacks are blocked.
🎯 Exploit Status
Exploitation requires network access to CUPS service but no authentication. The attack technique is simple but requires sustained connection.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.4.15
Vendor Advisory: https://github.com/OpenPrinting/cups/security/advisories/GHSA-8wpw-vfgm-qrrr
Restart Required: Yes
Instructions:
1. Backup current CUPS configuration. 2. Update CUPS to version 2.4.15 using your distribution's package manager. 3. Restart the cupsd service. 4. Verify the update was successful.
🔧 Temporary Workarounds
Network Access Restriction
linuxRestrict network access to CUPS service to trusted networks only
sudo ufw deny 631/tcp
sudo iptables -A INPUT -p tcp --dport 631 -j DROP
Rate Limiting
linuxImplement rate limiting for CUPS connections using network controls
sudo iptables -A INPUT -p tcp --dport 631 -m limit --limit 10/min --limit-burst 20 -j ACCEPT
🧯 If You Can't Patch
- Implement strict network segmentation to isolate CUPS services from untrusted networks
- Deploy network monitoring and intrusion detection systems to detect slow message attacks
🔍 How to Verify
Check if Vulnerable:
Check CUPS version with 'cups-config --version' or 'dpkg -l | grep cups' and compare to 2.4.15Check Version:
cups-config --version || dpkg -l | grep cups || rpm -q cupsVerify Fix Applied:
Verify CUPS version is 2.4.15 or higher and test printing functionality📡 Detection & Monitoring
Log Indicators:
- Unusually slow client connections in CUPS logs
- Multiple failed connection attempts from single IP
- Extended connection durations in access logs
Network Indicators:
- Sustained low-bandwidth connections to port 631
- Multiple TCP connections to CUPS from single source
SIEM Query:
source="cupsd" AND (connection_duration>300 OR bytes_per_second<10)🔗 References
- https://github.com/OpenPrinting/cups/commit/40008d76a001babbb9beb9d9d74b01a86fb6ddb4
- https://github.com/OpenPrinting/cups/releases/tag/v2.4.15
- https://github.com/OpenPrinting/cups/security/advisories/GHSA-8wpw-vfgm-qrrr
- http://www.openwall.com/lists/oss-security/2025/11/27/4
- https://github.com/OpenPrinting/cups/security/advisories/GHSA-8wpw-vfgm-qrrr
