CVE-2021-1334 – This vulnerability allows authenticated attacke... (How to Fix)

Q: What is the severity of CVE-2021-1334?

CVE-2021-1334 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 Cisco RV016, RV042, RV042G, RV082, RV320, or RV325 routers are affected.

📋 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 Cisco RV016, RV042, RV042G, RV082, RV320, or RV325 routers are affected.

💻 Affected Systems

Products:

Cisco Small Business RV016
Cisco Small Business RV042
Cisco Small Business RV042G
Cisco Small Business RV082
Cisco Small Business RV320
Cisco Small Business RV325

Versions: All versions prior to the fixed releases

Operating Systems: Embedded router OS

Default Config Vulnerable: ⚠️ Yes

Notes: Requires authenticated admin access to web management interface. Default configurations with admin credentials unchanged are vulnerable.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete system 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 - Web management interfaces exposed to internet are directly vulnerable to exploitation attempts.

🏢 Internal Only: MEDIUM - Internal attackers with admin credentials or credential theft could still exploit this vulnerability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires valid administrator credentials and ability to send crafted HTTP requests to the web interface.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: RV016: 4.2.3.14, RV042/RV042G: 4.2.3.14, RV082: 4.2.3.14, RV320: 1.5.1.11, RV325: 1.5.1.11

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

Restart Required: Yes

Instructions:

1. Download firmware from Cisco support portal. 2. Backup current configuration. 3. Upload firmware via web interface. 4. Apply update. 5. Reboot device. 6. Verify new firmware version.

🔧 Temporary Workarounds

Restrict Web Interface Access

all

Limit access to web management interface to trusted IP addresses only

Configure firewall rules to restrict access to router management IP/port

Disable Remote Management

all

Turn off web management interface access from WAN/external interfaces

Disable 'Remote Management' in router web interface settings

🧯 If You Can't Patch

Implement strong authentication controls with complex admin passwords and MFA if supported
Segment router management interface to isolated VLAN with strict access controls

🔍 How to Verify

Check if Vulnerable:

Check router firmware version via web interface: System Configuration > Status > Firmware Version

Check Version:

Check via web interface or SSH if enabled: show version

Verify Fix Applied:

Verify firmware version matches or exceeds patched versions listed in vendor advisory

📡 Detection & Monitoring

Log Indicators:

Multiple failed authentication attempts followed by successful login
Unusual HTTP POST requests to management interface
Device reboot logs without scheduled maintenance

Network Indicators:

Unusual outbound connections from router after admin login
HTTP traffic patterns matching exploit payloads

SIEM Query:

source="router_logs" (event="authentication_success" AND user="admin") AND (event="http_request" AND uri CONTAINS "/admin/")

📊 Metadata

CVE ID: CVE-2021-1334

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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