CVE-2021-34719
📋 TL;DR
This vulnerability allows authenticated local users with low privileges to execute arbitrary commands with elevated privileges on Cisco IOS XR devices. Attackers can exploit command injection flaws in the CLI to gain root-level access. Only devices running vulnerable versions of Cisco IOS XR Software are affected.
💻 Affected Systems
- Cisco IOS XR Software
📦 What is this software?
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
Ios Xr by Cisco
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to reconfigure network settings, intercept traffic, install persistent backdoors, or use the device as a pivot point to attack other network segments.
Likely Case
Privilege escalation leading to unauthorized configuration changes, network disruption, or data exfiltration from the compromised device.
If Mitigated
Limited impact due to proper access controls, network segmentation, and monitoring that would detect unusual privilege escalation attempts.
🎯 Exploit Status
Exploitation requires authenticated access but is relatively straightforward once an attacker has low-privilege credentials.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Cisco Security Advisory for specific fixed releases for different hardware platforms
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-privescal-dZYMrKf
Restart Required: Yes
Instructions:
1. Identify affected IOS XR devices. 2. Download appropriate fixed software from Cisco. 3. Schedule maintenance window. 4. Backup configuration. 5. Upgrade to fixed version. 6. Verify upgrade success and functionality.
🔧 Temporary Workarounds
Restrict CLI Access
cisco-ios-xrLimit low-privilege user access to CLI commands that could be exploited
configure terminal
aaa authorization exec default local
aaa authorization commands 15 default local
aaa authorization config-commands
end
🧯 If You Can't Patch
- Implement strict access controls and least privilege principles for all user accounts
- Monitor for unusual privilege escalation attempts and command execution patterns
🔍 How to Verify
Check if Vulnerable:
Check IOS XR version with 'show version' and compare against vulnerable versions listed in Cisco advisoryCheck Version:
show version | include Cisco IOS XR SoftwareVerify Fix Applied:
After upgrade, verify version with 'show version' and test that low-privilege users cannot execute privileged commands📡 Detection & Monitoring
Log Indicators:
- Unusual privilege escalation events
- Failed authorization attempts followed by successful privileged commands
- Commands executed from unexpected user accounts
Network Indicators:
- Unexpected configuration changes
- Unusual network traffic patterns from infrastructure devices
SIEM Query:
source="ios-xr" AND (event_type="authorization_failure" OR event_type="privilege_escalation")