CVE-2025-20160
📋 TL;DR
This vulnerability in Cisco IOS and IOS XE software allows attackers to intercept unencrypted TACACS+ authentication messages or impersonate TACACS+ servers due to improper shared secret validation. Attackers can view sensitive data or bypass authentication entirely. Organizations using TACACS+ authentication on affected Cisco devices are at risk.
💻 Affected Systems
- Cisco IOS Software
- Cisco IOS XE Software
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Complete network compromise through authentication bypass, allowing attackers to gain administrative access to network devices and potentially pivot to other systems.
Likely Case
Credential theft through interception of unencrypted TACACS+ traffic, leading to unauthorized access to network infrastructure.
If Mitigated
Limited impact if TACACS+ is not used or if proper network segmentation and monitoring are in place.
🎯 Exploit Status
Exploitation requires network access to intercept TACACS+ traffic or ability to impersonate TACACS+ server.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Cisco advisory for specific fixed versions
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-tacacs-hdB7thJw
Restart Required: Yes
Instructions:
1. Review Cisco advisory for affected versions. 2. Download and apply appropriate fixed software release. 3. Reload device to activate new software.
🔧 Temporary Workarounds
Disable TACACS+
allRemove TACACS+ configuration and use alternative authentication methods
no aaa group server tacacs+ <group-name>
no tacacs server <server-name>
no aaa authentication login default group tacacs+ local
Implement Network Controls
allRestrict TACACS+ traffic to trusted sources and use encryption
access-list 100 permit tcp host <tacacs-server> host <device> eq 49
access-list 100 deny ip any any
ip tacacs source-interface <interface>
🧯 If You Can't Patch
- Isolate TACACS+ servers and clients in a protected network segment with strict access controls
- Implement network monitoring for unusual TACACS+ traffic patterns and authentication attempts
🔍 How to Verify
Check if Vulnerable:
Check if TACACS+ is configured: 'show running-config | include tacacs' and verify device version against Cisco advisoryCheck Version:
show version | include VersionVerify Fix Applied:
Verify software version after upgrade: 'show version' and confirm TACACS+ functionality📡 Detection & Monitoring
Log Indicators:
- Failed TACACS+ authentication from unexpected sources
- Successful authentication from non-standard TACACS+ servers
- TACACS+ accounting records showing unusual access patterns
Network Indicators:
- Unencrypted TACACS+ traffic on network
- TACACS+ traffic from unexpected IP addresses
- Multiple authentication attempts from single source
SIEM Query:
source="network_device" AND (protocol="TACACS+" AND (src_ip NOT IN ["trusted_tacacs_servers"] OR dest_ip NOT IN ["authorized_devices"]))