Tenda CH22 Stack-Based Buffer Overflow Vulnerability

A critical stack-based buffer overflow vulnerability, identified as CVE-2026-5154, has been discovered in Tenda CH22 firmware version 1.0.0.1/1.If. The vulnerability resides within the fromSetCfm function in the /goform/setcfm file, a component of the Parameter Handler. Successful exploitation allows remote attackers to execute arbitrary code on the device. Publicly available exploits exist, increasing the risk of widespread exploitation. This vulnerability poses a significant threat to affected Tenda CH22 devices, potentially leading to complete system compromise.

Attack Chain

1. Attacker identifies a Tenda CH22 device running firmware version 1.0.0.1/1.If.
2. The attacker crafts a malicious HTTP POST request targeting the /goform/setcfm endpoint.
3. The request includes the funcname argument containing a string exceeding the buffer size allocated to it.
4. The fromSetCfm function processes the malicious funcname argument without proper bounds checking.
5. The oversized funcname value overflows the stack buffer, overwriting adjacent memory regions.
6. The attacker overwrites the return address on the stack with an address pointing to malicious code or a ROP chain.
7. The fromSetCfm function returns, causing execution to jump to the attacker-controlled address.
8. The attacker gains arbitrary code execution on the device, potentially leading to full system compromise.

Impact

Successful exploitation of this vulnerability allows a remote, unauthenticated attacker to execute arbitrary code on the affected Tenda CH22 device. This can result in complete device compromise, allowing the attacker to control the device, steal sensitive information, or use the device as a foothold for further attacks on the network. Given the availability of public exploits, a large number of devices could be compromised if left unpatched.

Recommendation

• Monitor web server logs for suspicious POST requests to /goform/setcfm with unusually long funcname parameters, using the provided Sigma rule.
• Implement rate limiting on requests to /goform/setcfm to mitigate potential brute-force exploitation attempts.
• Apply any available patches or firmware updates from Tenda to address CVE-2026-5154.