CVE-2026-5550: Tenda AC10 Buffer Overflow Vulnerability

CVE-2026-5550 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda AC10 routers running firmware version 16.03.10.10_multi_TDE01. This vulnerability affects the fromSysToolChangePwd function within the /bin/httpd binary, where improper handling of user-supplied input leads to memory corruption. The vulnerability can be exploited remotely by authenticated attackers to potentially achieve arbitrary code execution on affected devices.

Critical Impact

Remote attackers with low privileges can exploit this stack-based buffer overflow to compromise Tenda AC10 routers, potentially gaining full control of the device, intercepting network traffic, or using the compromised router as a pivot point for further network attacks.

Affected Products

• Tenda AC10 firmware version 16.03.10.10_multi_TDE01
• Tenda AC10v4 variants with vulnerable firmware
• Multiple endpoints running the affected /bin/httpd binary

Discovery Timeline

• April 5, 2026 - CVE-2026-5550 published to NVD
• April 7, 2026 - Last updated in NVD database

Technical Details for CVE-2026-5550

Vulnerability Analysis

This vulnerability exists in the fromSysToolChangePwd function, which is responsible for handling password change operations on the device's web management interface. The function fails to properly validate the length of user-supplied input before copying it to a fixed-size stack buffer, resulting in a classic stack-based buffer overflow condition.

The vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), indicating that the affected code performs operations outside the intended boundaries of a memory buffer. This type of vulnerability is particularly dangerous in embedded devices like routers, which often lack modern exploit mitigations such as ASLR, stack canaries, and non-executable stacks.

An attacker can leverage this vulnerability by sending specially crafted HTTP requests to the device's web interface. The attack requires network access and low-level authentication, but successful exploitation could allow the attacker to overwrite the return address on the stack, redirect execution flow, and achieve arbitrary code execution with the privileges of the httpd process.

Root Cause

The root cause of this vulnerability is improper bounds checking in the fromSysToolChangePwd function. When processing password change requests, the function uses unsafe string manipulation operations that do not verify whether the input data exceeds the allocated stack buffer size. This allows an attacker to supply an overly long input string that overflows the buffer and overwrites adjacent memory, including the function's return address.

Attack Vector

The attack is conducted remotely over the network through the device's HTTP-based management interface. An attacker would need to craft a malicious HTTP POST request targeting the password change functionality with an oversized payload designed to trigger the buffer overflow. The attack requires low-level authentication (PR:L), but no user interaction is necessary for successful exploitation.

The vulnerability affects the confidentiality, integrity, and availability of the target system, as successful exploitation could allow the attacker to read sensitive data, modify system configurations, or cause the device to crash or become unresponsive.

For detailed technical analysis of this vulnerability, refer to the GitHub Vulnerability Findings and VulDB entry #355314.

Detection Methods for CVE-2026-5550

Indicators of Compromise

• Unexpected crashes or reboots of the Tenda AC10 router
• Anomalous HTTP POST requests to password change endpoints containing oversized payloads
• Unusual outbound network connections from the router to unknown IP addresses
• Modified router configurations or unauthorized administrative accounts

Detection Strategies

• Monitor HTTP traffic to the router's management interface for abnormally large POST request bodies
• Implement network intrusion detection rules to identify buffer overflow exploitation patterns targeting /bin/httpd
• Deploy log analysis to detect repeated authentication attempts followed by suspicious activity
• Use SentinelOne Singularity to monitor for anomalous process behavior on network infrastructure devices

Monitoring Recommendations

• Enable logging on the Tenda AC10 web interface and forward logs to a centralized SIEM solution
• Set up alerts for HTTP requests exceeding normal size thresholds to the management interface
• Monitor for changes to device firmware or configuration files that may indicate successful exploitation
• Implement network segmentation to limit exposure of router management interfaces

How to Mitigate CVE-2026-5550

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management if not required for operational purposes
• Place affected Tenda AC10 devices behind a firewall that blocks external access to port 80/443
• Monitor Tenda's official channels for firmware updates addressing this vulnerability

Patch Information

As of the last update on April 7, 2026, no official patch has been released by Tenda for this vulnerability. Organizations should monitor the Tenda Official Website for security advisories and firmware updates. In the interim, implementing network-level access controls is strongly recommended to reduce the attack surface.

Workarounds

• Configure firewall rules to restrict management interface access to internal networks only
• Implement strong network segmentation to isolate IoT and network infrastructure devices
• Consider replacing affected devices with alternative products that receive regular security updates
• Deploy a VPN solution for remote administration rather than exposing the management interface directly

# Configuration example - iptables rules to restrict management access
# Allow management access only from trusted admin network
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP