Totolink N300RT Buffer Overflow Vulnerability (CVE-2026-7219)

A buffer overflow vulnerability, identified as CVE-2026-7219, has been discovered in Totolink N300RT router firmware version 3.4.0-B20250430. The vulnerability resides within the /boafrm/formIpQoS file and is triggered by manipulating the entry_name argument. An attacker can exploit this flaw remotely to potentially execute arbitrary code on the device. Publicly available exploit code exists, increasing the risk of exploitation. This vulnerability poses a significant threat to devices running the affected firmware, potentially allowing attackers to gain unauthorized access and control over the router.

Attack Chain

1. An attacker identifies a Totolink N300RT device running firmware version 3.4.0-B20250430.
2. The attacker crafts a malicious HTTP request targeting the /boafrm/formIpQoS file.
3. The crafted request includes a payload designed to overflow the buffer associated with the entry_name argument.
4. The router’s web server processes the malicious request, leading to a buffer overflow condition.
5. The attacker overwrites adjacent memory regions, potentially including return addresses or other critical data.
6. Upon function return, the overwritten return address is used, diverting execution flow to attacker-controlled code.
7. The attacker gains arbitrary code execution on the device.
8. The attacker can then use this access to modify router settings, intercept network traffic, or establish a persistent backdoor.

Impact

Successful exploitation of this vulnerability allows a remote attacker to execute arbitrary code on the Totolink N300RT device. This could lead to complete compromise of the router, enabling attackers to monitor network traffic, change DNS settings, or use the device as part of a botnet. Given the number of Totolink N300RT devices deployed, this vulnerability could have a widespread impact, especially for home and small business users.

Recommendation

• Monitor web server logs for requests targeting /boafrm/formIpQoS with unusually long entry_name parameters to detect potential exploitation attempts. Implement the Sigma rule Detect Suspicious Totolink FormIpQoS Requests.
• Apply firmware updates as soon as they are released by Totolink to patch CVE-2026-7219.
• Implement network segmentation to limit the impact of a compromised router on other devices on the network.
• Consider using a web application firewall (WAF) to filter out malicious requests targeting the router’s web interface and activate the Detect Large POST Requests to Router Config Pages Sigma rule.