CVE-2021-1348 – This vulnerability allows authenticated remote ... (How to Fix)

Q: What is the severity of CVE-2021-1348?

CVE-2021-1348 has a CVSS score of 7.2 (HIGH). This vulnerability allows authenticated remote attackers to execute arbitrary code as root or cause denial of service on affected Cisco Small Business routers. Attackers need valid administrator credentials to exploit improper input validation in the web management interface. Organizations using these routers for network infrastructure are affected.

📋 TL;DR

This vulnerability allows authenticated remote attackers to execute arbitrary code as root or cause denial of service on affected Cisco Small Business routers. Attackers need valid administrator credentials to exploit improper input validation in the web management interface. Organizations using these routers for network infrastructure are affected.

💻 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: Affects web-based management interface; requires admin credentials for exploitation

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete device compromise with root-level arbitrary code execution, allowing attacker persistence, network pivoting, and data interception.

🟠

Likely Case

Device reboot causing temporary network outage and service disruption for connected users and systems.

🟢

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 valid admin credentials but involves simple crafted HTTP requests

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: RV016: 4.2.3.14, RV042/RV042G: 4.2.3.14, RV082: 4.2.3.14, RV320/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 website. 2. Log into router web interface. 3. Navigate to Administration > Firmware Upgrade. 4. Upload and install new firmware. 5. Reboot router after installation.

🔧 Temporary Workarounds

Restrict Web Management Access

all

Limit access to web management interface to trusted IP addresses only

Disable Remote Management

all

Turn off web management interface from WAN/Internet-facing interfaces

🧯 If You Can't Patch

Implement strict access controls to limit who can access the web management interface
Use strong, unique admin passwords and enable multi-factor authentication if available

🔍 How to Verify

Check if Vulnerable:

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

Check Version:

No CLI command; check via web interface or SNMP

Verify Fix Applied:

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

📡 Detection & Monitoring

Log Indicators:

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

Network Indicators:

HTTP traffic to router management interface from unexpected sources
Multiple HTTP requests with malformed parameters

SIEM Query:

source="router_logs" AND (event="authentication_success" AND user="admin" AND src_ip NOT IN trusted_ips) OR (event="device_reboot" AND NOT maintenance_window)

📊 Metadata

CVE ID: CVE-2021-1348

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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