CVE-2021-1392

Q: What is the severity of CVE-2021-1392?

CVE-2021-1392 has a CVSS score of 7.8 (HIGH). This vulnerability allows authenticated local attackers on Cisco IOS/IOS XE devices to retrieve Common Industrial Protocol (CIP) passwords via a misconfigured CLI command. Attackers can then use these credentials to remotely reconfigure devices as administrative users. Organizations using affected Cisco networking equipment with CIP enabled are at risk.

7.8 HIGH

📋 TL;DR

This vulnerability allows authenticated local attackers on Cisco IOS/IOS XE devices to retrieve Common Industrial Protocol (CIP) passwords via a misconfigured CLI command. Attackers can then use these credentials to remotely reconfigure devices as administrative users. Organizations using affected Cisco networking equipment with CIP enabled are at risk.

💻 Affected Systems

Products:

Cisco IOS
Cisco IOS XE

Versions: Multiple versions - see Cisco advisory for specific affected releases

Operating Systems: Cisco IOS, Cisco IOS XE

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects devices with Common Industrial Protocol (CIP) functionality enabled. Industrial networking equipment in manufacturing, energy, and critical infrastructure sectors are most vulnerable.

📦 What is this software?

Ios Xe by Cisco

Cisco IOS XE is Cisco's modern network operating system running on enterprise routers, switches, and wireless controllers deployed across corporate networks, data centers, branch offices, and service provider infrastructure worldwide. As the evolution of Cisco IOS, IOS XE provides a Linux-based modu...

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⚠️ Risk & Real-World Impact

🔴

Worst Case

Full administrative compromise of industrial control systems, allowing attackers to reconfigure critical infrastructure devices, disrupt operations, or establish persistent access.

🟠

Likely Case

Unauthorized administrative access to network devices, enabling configuration changes, traffic interception, or lateral movement within industrial networks.

🟢

If Mitigated

Limited impact if proper access controls, network segmentation, and monitoring are in place to detect unauthorized configuration changes.

🌐 Internet-Facing: MEDIUM - While exploitation requires local access, retrieved credentials could be used for remote attacks if devices are internet-accessible.

🏢 Internal Only: HIGH - Industrial control systems often have privileged access requirements, and compromised credentials could severely impact operations.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: LIKELY

Unauthenticated Exploit: ✅ No

Complexity: LOW

Exploitation requires authenticated local access but involves simple CLI command execution. Credential retrieval enables subsequent remote attacks.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Refer to Cisco Security Advisory for fixed releases

Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-XE-SAP-OPLbze68

Restart Required: Yes

Instructions:

1. Review Cisco Security Advisory for affected versions. 2. Upgrade to fixed software releases. 3. Schedule maintenance window for device restart. 4. Verify fix after upgrade.

🔧 Temporary Workarounds

Restrict CLI Access

all

Limit access to CLI commands for non-administrative users using role-based access control

configure terminal
privilege exec level 15 show cip security
end

Disable Unused CIP Features

all

If CIP functionality is not required, disable it to remove attack surface

configure terminal
no cip security
end

🧯 If You Can't Patch

Implement strict access controls and monitor for unauthorized 'show cip security' command usage
Segment industrial networks and restrict administrative access to trusted management networks only

🔍 How to Verify

Check if Vulnerable:

Check if device runs affected IOS/IOS XE version and has CIP enabled using 'show version' and 'show running-config | include cip'

Check Version:

show version

Verify Fix Applied:

After patching, verify fixed version with 'show version' and test that 'show cip security' command no longer reveals passwords

📡 Detection & Monitoring

Log Indicators:

Unauthorized 'show cip security' command execution in system logs
Unexpected configuration changes following credential access

Network Indicators:

Unusual administrative connections to industrial devices
Configuration changes from unexpected sources

SIEM Query:

source="cisco-ios" command="show cip security" OR command="configure terminal"

📊 Metadata

CVE ID: CVE-2021-1392

CVSS v3 Score: 7.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-522

Published: March 24, 2021

Last Updated: November 21, 2024

🔗 References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-XE-SAP-OPLbze68 Vendor Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-XE-SAP-OPLbze68 Vendor Advisory

📋 TL;DR

💻 Affected Systems

📦 What is this software?

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