CVE-2021-1342 – This vulnerability allows authenticated attacke... (How to Fix)

Q: What is the severity of CVE-2021-1342?

CVE-2021-1342 has a CVSS score of 7.2 (HIGH). This vulnerability allows authenticated attackers with administrator credentials to execute arbitrary code as root or cause denial of service on affected Cisco Small Business routers. The issue stems from improper input validation in the web management interface. Organizations using these specific router models are at risk.

📋 TL;DR

This vulnerability allows authenticated attackers with administrator credentials to execute arbitrary code as root or cause denial of service on affected Cisco Small Business routers. The issue stems from improper input validation in the web management interface. Organizations using these specific router models are at risk.

💻 Affected Systems

Products:

Cisco Small Business RV016
RV042
RV042G
RV082
RV320
RV325 Routers

Versions: All versions prior to the fixed releases

Operating Systems: Embedded router OS

Default Config Vulnerable: ⚠️ Yes

Notes: Requires valid administrator credentials to exploit

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete device compromise with root-level arbitrary code execution, allowing full control of the router and potential lateral movement into connected networks.

🟠

Likely Case

Denial of service through device reboots disrupting network connectivity for connected users and services.

🟢

If Mitigated

Limited impact if strong authentication controls prevent unauthorized access to admin credentials.

🌐 Internet-Facing: HIGH

🏢 Internal Only: MEDIUM

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: LOW

Exploitation requires authenticated access but is straightforward once credentials are obtained

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Check Cisco advisory for specific fixed versions per model

Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-rv-overflow-ghZP68yj

Restart Required: Yes

Instructions:

1. Access router web interface 2. Navigate to Administration > Firmware Upgrade 3. Download latest firmware from Cisco 4. Upload and install firmware 5. Reboot router

🔧 Temporary Workarounds

Restrict Web Interface Access

all

Limit access to the web management interface to trusted IP addresses only

Strong Authentication Controls

all

Implement complex passwords, multi-factor authentication, and regular credential rotation

🧯 If You Can't Patch

Isolate affected routers in separate network segments with strict firewall rules
Disable remote web management and require physical/local access only

🔍 How to Verify

Check if Vulnerable:

Check router firmware version against Cisco advisory and compare with fixed versions

Check Version:

Login to web interface > Status > Router > Firmware Version

Verify Fix Applied:

Confirm firmware version matches or exceeds the patched version listed in Cisco advisory

📡 Detection & Monitoring

Log Indicators:

Multiple failed login attempts followed by successful login and unusual HTTP requests
Device reboot logs without scheduled maintenance

Network Indicators:

Unusual HTTP traffic patterns to router management interface
Sudden device reboots disrupting connectivity

SIEM Query:

source="router_logs" AND (event="authentication_success" OR event="device_reboot") AND user="admin"

📊 Metadata

CVE ID: CVE-2021-1342

CVSS v3 Score: 7.2 (HIGH)

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

CWE: CWE-121

Published: February 4, 2021

Last Updated: November 21, 2024

🔗 References

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🔗 Related Vulnerabilities

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