CVE-2025-40634 Overview
A critical stack-based buffer overflow vulnerability has been identified in the conn-indicator binary on TP-Link Archer AX50 routers. This binary runs with root privileges, and the vulnerability exists in firmware versions prior to 1.0.15 build 241203 rel61480. The flaw allows an attacker to execute arbitrary code on the affected device over both LAN and WAN networks, potentially leading to complete device compromise.
Critical Impact
This vulnerability enables remote code execution with root privileges on affected TP-Link Archer AX50 routers, allowing attackers to gain complete control over the device from network-accessible positions.
Affected Products
- TP-Link Archer AX50 Router firmware versions prior to 1.0.15 build 241203 rel61480
- conn-indicator binary component running as root
- Network-connected devices accessible via LAN or WAN
Discovery Timeline
- 2025-05-20 - CVE-2025-40634 published to NVD
- 2025-05-21 - Last updated in NVD database
Technical Details for CVE-2025-40634
Vulnerability Analysis
This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow). The conn-indicator binary on the TP-Link Archer AX50 router contains a stack-based buffer overflow that can be exploited remotely. Since the binary operates with root privileges, successful exploitation grants the attacker complete administrative control over the router.
The attack can be conducted over both LAN and WAN networks, significantly expanding the attack surface. While the attack complexity is elevated due to the nature of the exploitation, no user interaction or prior authentication is required, making this a particularly dangerous vulnerability for exposed devices.
Root Cause
The root cause of this vulnerability is improper bounds checking in the conn-indicator binary. When processing input data, the binary fails to properly validate the length of data being written to a stack buffer. This allows an attacker to overflow the buffer and overwrite adjacent memory on the stack, including return addresses and other control flow data.
Stack-based buffer overflows are a classic vulnerability class where insufficient input validation allows data to exceed allocated buffer boundaries. In embedded systems like routers, these vulnerabilities are particularly severe due to limited memory protection mechanisms and the elevated privileges typically associated with system binaries.
Attack Vector
The attack vector is network-based, accessible from both local area network (LAN) and wide area network (WAN) interfaces. An attacker can craft malicious network packets targeting the conn-indicator binary to trigger the buffer overflow condition.
The exploitation scenario involves:
- Identifying a vulnerable TP-Link Archer AX50 router running firmware prior to 1.0.15 build 241203 rel61480
- Crafting specially formatted network traffic designed to overflow the stack buffer in conn-indicator
- Injecting malicious code or shellcode that executes with root privileges once the overflow corrupts the stack
- Achieving arbitrary code execution with full administrative control over the router
For detailed technical information about this vulnerability, refer to the INCIBE Notice: Buffer Overflow on TP-Link Archer AX50.
Detection Methods for CVE-2025-40634
Indicators of Compromise
- Unexpected network connections originating from the router to external command and control servers
- Anomalous traffic patterns involving the conn-indicator service or related ports
- Unexplained router configuration changes or unauthorized administrative access
- Suspicious firmware modifications or additional binaries present on the device
Detection Strategies
- Monitor network traffic for malformed or oversized packets targeting TP-Link router services
- Implement network intrusion detection signatures for known buffer overflow exploit patterns targeting embedded devices
- Deploy network anomaly detection to identify unusual outbound connections from router IP addresses
- Conduct regular firmware version audits to identify devices running vulnerable firmware
Monitoring Recommendations
- Enable logging on network perimeter devices to capture traffic to and from router management interfaces
- Configure alerts for any administrative changes made to router configurations
- Monitor for DNS queries or connections to known malicious infrastructure from router devices
- Implement network segmentation to limit exposure of router management interfaces
How to Mitigate CVE-2025-40634
Immediate Actions Required
- Update TP-Link Archer AX50 firmware to version 1.0.15 build 241203 rel61480 or later immediately
- Disable WAN-side management access if remote administration is not required
- Implement network segmentation to isolate router management interfaces from untrusted networks
- Review router logs for any signs of compromise or unauthorized access attempts
Patch Information
TP-Link has released firmware version 1.0.15 build 241203 rel61480 which addresses this vulnerability. Administrators should download the latest firmware directly from the official TP-Link support website and apply it to affected devices. Ensure that firmware updates are verified and obtained only from official sources to prevent supply chain attacks.
For additional information, consult the INCIBE Notice: Buffer Overflow on TP-Link Archer AX50.
Workarounds
- Restrict network access to the router's management interfaces using firewall rules
- Disable remote management features if they are not required for operations
- Implement access control lists (ACLs) to limit which IP addresses can communicate with router services
- Deploy network-based intrusion prevention systems (IPS) to block known exploit attempts
# Configuration example - Restrict management access via firewall
# Block WAN access to router management ports (example using iptables on upstream firewall)
iptables -A INPUT -i eth0 -p tcp --dport 80 -s 0.0.0.0/0 -j DROP
iptables -A INPUT -i eth0 -p tcp --dport 443 -s 0.0.0.0/0 -j DROP
iptables -A INPUT -i eth0 -p tcp --dport 22 -s 0.0.0.0/0 -j DROP
# Allow management only from trusted internal networks
iptables -A INPUT -i eth1 -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -i eth1 -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
