CVE-2022-25064: TP-Link TL-WR840N Firmware RCE Flaw

CVE-2022-25064 Overview

CVE-2022-25064 is a critical remote code execution (RCE) vulnerability discovered in the TP-LINK TL-WR840N(ES)_V6.20_180709 router firmware. The vulnerability exists within the oal_wan6_setIpAddr function, which fails to properly sanitize user-supplied input, allowing unauthenticated attackers to execute arbitrary commands on the affected device with root privileges.

Critical Impact

This vulnerability enables unauthenticated remote attackers to execute arbitrary code on vulnerable TP-LINK routers, potentially leading to complete device compromise, network infiltration, and use of the device in botnet operations.

Affected Products

• TP-LINK TL-WR840N Firmware Version 6.20_180709
• TP-LINK TL-WR840N Hardware (ES variant)
• TP-LINK TL-WR840N_V6 Series Routers

Discovery Timeline

• February 25, 2022 - CVE-2022-25064 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-25064

Vulnerability Analysis

This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly known as OS Command Injection. The vulnerable function oal_wan6_setIpAddr processes IPv6 address input without adequate validation or sanitization before passing it to system commands. An attacker can craft malicious input containing shell metacharacters or command separators that, when processed by the function, result in arbitrary command execution on the underlying Linux-based operating system of the router.

The network-accessible nature of this vulnerability means that any attacker who can reach the router's management interface can exploit this flaw without requiring any authentication credentials. Successful exploitation grants the attacker complete control over the router with root-level privileges, as embedded device services typically run with elevated permissions.

Root Cause

The root cause of CVE-2022-25064 lies in the oal_wan6_setIpAddr function's failure to implement proper input validation and sanitization for IPv6 address parameters. When the function constructs system commands using user-supplied data, it does not escape or filter special characters such as semicolons (;), pipes (|), backticks, or other shell metacharacters. This allows an attacker to break out of the intended command context and inject additional malicious commands.

Attack Vector

The attack vector is network-based, requiring no prior authentication or user interaction. An attacker can exploit this vulnerability by:

1. Accessing the router's web management interface (typically on the local network, or exposed to the internet if misconfigured)
2. Submitting a specially crafted request to the vulnerable endpoint that handles IPv6 address configuration
3. Including shell metacharacters within the IPv6 address input field
4. The malicious payload is passed to oal_wan6_setIpAddr and subsequently executed with root privileges

The vulnerability manifests when user-controlled data in the IPv6 address input field is passed unsanitized to system shell commands. Attackers can inject command separators followed by arbitrary commands to achieve remote code execution. For detailed technical analysis of the exploitation mechanism, refer to the vulnerability analysis documentation.

Detection Methods for CVE-2022-25064

Indicators of Compromise

• Unexpected outbound network connections from the router to unknown external IP addresses
• Modified router configuration settings or unauthorized administrative accounts
• Unusual processes running on the router that are not part of standard firmware
• Network traffic anomalies suggesting the router is participating in botnet activities or scanning operations

Detection Strategies

• Monitor web server logs on the router for suspicious requests containing shell metacharacters in IPv6 address parameters
• Implement network intrusion detection rules to identify command injection patterns in HTTP traffic to router management interfaces
• Deploy behavioral analysis to detect anomalous router activity such as unexpected DNS queries or outbound connections
• Regularly compare router configuration against known-good baselines to detect unauthorized modifications

Monitoring Recommendations

• Enable logging on network firewalls to track all traffic to and from router management interfaces
• Implement alerting for any external access attempts to router administration ports
• Monitor for firmware integrity changes using hash verification where supported
• Track DHCP and DNS changes that may indicate router compromise

How to Mitigate CVE-2022-25064

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote administration features if not absolutely required
• Place the router behind a properly configured firewall that blocks external access to management ports
• Monitor the TP-LINK support site for firmware updates addressing this vulnerability

Patch Information

At the time of publication, users should check the TP-Link Official Site for updated firmware releases that address CVE-2022-25064. It is critical to update to the latest available firmware version for the TL-WR840N(ES)_V6 device as soon as a patch becomes available. Firmware version 6.20_180709 and potentially earlier versions are confirmed vulnerable.

Workarounds

• Disable the WAN IPv6 configuration interface if IPv6 functionality is not required
• Implement network segmentation to isolate the router's management interface from untrusted networks
• Use a VPN to access router administration rather than exposing the interface directly
• Consider replacing the vulnerable device with a model that receives regular security updates

# Network access restriction example (firewall rule)
# Block external access to router management interface
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP