CVE-2026-5155 is a stack-based buffer overflow vulnerability identified in the Tenda CH22 router firmware version 1.0.0.1. The flaw exists in the fromAdvSetWan function within the /goform/AdvSetWan endpoint, part of the parameter handling component. The vulnerability is triggered by manipulating the wanmode argument, which is improperly validated or sanitized, leading to a stack overflow condition. This overflow can overwrite the stack memory, potentially allowing an attacker to execute arbitrary code remotely. The vulnerability requires no user interaction and no prior authentication, making it exploitable over the network by unauthenticated attackers. The CVSS 4.0 score of 8.7 reflects its high severity, with attack vector being network (AV:N), low attack complexity (AC:L), no privileges required (PR:L), and no user interaction (UI:N). The impact covers high confidentiality, integrity, and availability consequences, meaning attackers could gain control over the device, intercept or alter network traffic, or disrupt network services. Although no active exploits in the wild have been reported, the public availability of exploit code increases the urgency for mitigation. The vulnerability affects a specific firmware version, indicating that upgrading or patching the device firmware is critical. The lack of available patches at the time of reporting suggests that users must implement interim mitigations to reduce exposure.

The exploitation of this vulnerability could have severe consequences for organizations relying on Tenda CH22 routers. Successful attacks can lead to full device compromise, allowing attackers to execute arbitrary code with elevated privileges. This can result in unauthorized access to internal networks, interception or manipulation of sensitive data, disruption of network services, and potential lateral movement within corporate environments. For home users, compromised routers can be used as entry points for broader attacks or to launch distributed denial-of-service (DDoS) attacks. Given the device’s role in managing WAN connections, attackers could manipulate network configurations, causing outages or redirecting traffic to malicious endpoints. The high severity and ease of exploitation increase the risk of widespread attacks, especially in environments where these devices are deployed without timely firmware updates or adequate network segmentation.

1. Immediately check for and apply any official firmware updates or patches released by Tenda addressing CVE-2026-5155. 2. If patches are not yet available, restrict remote access to the router’s management interfaces by implementing firewall rules or access control lists limiting connections to trusted IP addresses. 3. Disable remote management features if not required, especially WAN-side access to the /goform/AdvSetWan endpoint. 4. Monitor network traffic for unusual activity or attempts to exploit the wanmode parameter, using intrusion detection systems capable of detecting buffer overflow attempts. 5. Segment networks to isolate critical infrastructure and reduce the impact of a compromised router. 6. Regularly audit router configurations and logs to detect unauthorized changes or access. 7. Educate network administrators about the vulnerability and ensure rapid response plans are in place for potential exploitation. 8. Consider deploying network-level protections such as web application firewalls or anomaly detection systems that can block malformed requests targeting the vulnerable endpoint.