CVE-2025-20336
📋 TL;DR
An information disclosure vulnerability in Cisco phone systems allows unauthenticated remote attackers to access sensitive information when Web Access is enabled. This affects Cisco Desk Phone 9800 Series, IP Phone 7800/8800 Series, and Video Phone 8875. Attackers can exploit this by sending crafted packets to vulnerable devices.
💻 Affected Systems
- Cisco Desk Phone 9800 Series
- Cisco IP Phone 7800 Series
- Cisco IP Phone 8800 Series
- Cisco Video Phone 8875
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers gain access to sensitive device information including configuration details, credentials, or call logs that could facilitate further attacks.
Likely Case
Unauthorized access to device information that could be used for reconnaissance or to understand network topology.
If Mitigated
Limited impact if Web Access is disabled or proper network segmentation is in place.
🎯 Exploit Status
Exploitation requires Web Access to be enabled and involves sending crafted packets to the device IP address.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Cisco advisory for specific firmware versions
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-phone-write-g3kcC5Df
Restart Required: Yes
Instructions:
1. Review Cisco advisory for affected firmware versions. 2. Download and apply the latest firmware update from Cisco. 3. Reboot affected phones after update.
🔧 Temporary Workarounds
Disable Web Access
allDisable Web Access feature on affected phones to prevent exploitation
Navigate to phone web interface > Administration > Web Access > Disable
Network Segmentation
allRestrict network access to phone management interfaces
Configure firewall rules to block external access to phone web interfaces
🧯 If You Can't Patch
- Disable Web Access on all affected phones immediately
- Implement strict network segmentation to isolate phone management interfaces from untrusted networks
🔍 How to Verify
Check if Vulnerable:
Check if Web Access is enabled on affected phones via web interface or configuration filesCheck Version:
Check phone web interface > Status > Firmware Version or use CLI if availableVerify Fix Applied:
Verify firmware version is updated to patched version and Web Access remains disabled if not required📡 Detection & Monitoring
Log Indicators:
- Unusual access patterns to phone web interfaces
- Multiple failed or successful access attempts from unusual IPs
Network Indicators:
- Crafted HTTP/HTTPS packets targeting phone web interfaces
- Traffic to phone management ports from unauthorized sources
SIEM Query:
source_ip NOT IN (authorized_management_ips) AND dest_port IN (80,443,8080) AND dest_ip IN (phone_ips)