CVE-2023-20259
📋 TL;DR
An unauthenticated remote attacker can send crafted HTTP requests to a specific API endpoint in Cisco Unified Communications products, causing high CPU utilization that leads to denial of service. This affects web management access and call processing delays. The vulnerability exists in multiple Cisco UC products when running vulnerable software versions.
💻 Affected Systems
- Cisco Unified Communications Manager
- Cisco Unified Communications Manager Session Management Edition
- Cisco Unified Communications Manager IM & Presence Service
- Cisco Unity Connection
📦 What is this software?
Unified Communications Manager Im \& Presence Service by Cisco
View all CVEs affecting Unified Communications Manager Im \& Presence Service →
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service affecting both management access and call processing capabilities, potentially disrupting business communications.
Likely Case
Intermittent service degradation with management interface becoming unresponsive and call processing delays during attack periods.
If Mitigated
Minimal impact if network controls block unauthorized access to the vulnerable API endpoint.
🎯 Exploit Status
Simple HTTP request to specific endpoint with no authentication required makes exploitation trivial.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Multiple fixed versions available - refer to Cisco advisory for specific product fixes
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-cucm-apidos-PGsDcdNF
Restart Required: Yes
Instructions:
1. Review Cisco advisory for specific fixed versions for your product. 2. Download appropriate patch from Cisco Software Center. 3. Apply patch following Cisco UC upgrade procedures. 4. Restart affected services or devices as required.
🔧 Temporary Workarounds
Network Access Control
allRestrict access to the vulnerable API endpoint using network controls
Configure firewall/ACL to block external access to port 8443/tcp on affected devices
Implement network segmentation to limit internal access
🧯 If You Can't Patch
- Implement strict network segmentation to isolate UC systems from untrusted networks
- Deploy rate limiting and DoS protection mechanisms at network perimeter
🔍 How to Verify
Check if Vulnerable:
Check current software version against vulnerable versions listed in Cisco advisoryCheck Version:
From CLI: show version active | include VersionVerify Fix Applied:
Verify installed version matches or exceeds fixed versions in Cisco advisory📡 Detection & Monitoring
Log Indicators:
- High CPU utilization alerts
- Unusual HTTP requests to API endpoints
- Web management interface access failures
Network Indicators:
- Spike in HTTP traffic to port 8443
- Repeated requests to specific API endpoints from single sources
SIEM Query:
source="cisco-uc" AND (http_request_uri CONTAINS "/api/v1/" OR cpu_utilization > 90)