CVE-2025-5901 in T10
Summary
by MITRE • 06/10/2025
A vulnerability has been found in TOTOLINK T10 4.1.8cu.5207 and classified as critical. This vulnerability affects the function UploadCustomModule of the file /cgi-bin/cstecgi.cgi of the component POST Request Handler. The manipulation of the argument File leads to buffer overflow. The attack can be initiated remotely. The exploit has been disclosed to the public and may be used.
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Analysis
by VulDB Data Team • 06/16/2025
The vulnerability identified as CVE-2025-5901 represents a critical buffer overflow flaw within the TOTOLINK T10 router firmware version 4.1.8cu.5207. This security issue resides in the UploadCustomModule function of the /cgi-bin/cstecgi.cgi component, which serves as the primary interface for handling POST requests to the device. The flaw manifests when processing the File argument, creating an exploitable condition that allows attackers to manipulate memory structures beyond their intended boundaries. The vulnerability's classification as critical stems from its remote exploitability and the fact that a public exploit has already been disclosed, significantly increasing the risk to affected systems. The affected device operates with a web-based management interface that exposes the vulnerable POST handler function, making it accessible to attackers without requiring physical access to the device. This remote attack vector creates a substantial threat surface as the vulnerability can be leveraged from any location with network connectivity to the affected router.
The technical nature of this buffer overflow vulnerability places it squarely within the scope of CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The flaw occurs in the POST Request Handler component, specifically during the processing of uploaded module files, where the application fails to properly validate or limit the size of incoming data. When an attacker submits a maliciously crafted File parameter, the system attempts to store this data in a fixed-size buffer without adequate size verification, leading to memory corruption that can result in arbitrary code execution or system instability. The vulnerability's exploitation requires only a single HTTP POST request to the affected cgi-bin endpoint, making it particularly dangerous as it can be triggered through automated scanning tools or manual exploitation. The buffer overflow condition creates opportunities for attackers to overwrite return addresses, function pointers, or other critical memory structures that control program execution flow.
The operational impact of CVE-2025-5901 extends far beyond simple denial of service conditions, as it provides potential attackers with a pathway to achieve full system compromise. Successful exploitation could enable remote code execution, allowing threat actors to install backdoors, modify router configurations, redirect traffic, or establish persistent access to networks. The affected TOTOLINK T10 devices typically serve as primary network gateways, making them attractive targets for attackers seeking to establish footholds within larger networks. The vulnerability's remote exploitability means that attackers do not require physical access or network credentials to initiate attacks, significantly broadening the potential attack surface. Organizations using these devices may experience complete loss of network control, data interception, or redirection of network traffic through the compromised router. The public disclosure of exploitation techniques further compounds the risk, as it provides threat actors with readily available methods to target vulnerable installations, potentially affecting thousands of devices across multiple network environments.
Mitigation strategies for CVE-2025-5901 should prioritize immediate firmware updates from TOTOLINK, as this represents the most effective defense against exploitation. Network administrators should implement network segmentation and access controls to limit exposure of affected devices to untrusted networks, while also deploying intrusion detection systems to monitor for exploitation attempts. The implementation of web application firewalls can provide additional protection by filtering suspicious POST requests to the vulnerable endpoint, though this approach should not be considered a complete solution. Device hardening measures including disabling unnecessary services, restricting administrative access, and implementing strong authentication mechanisms can help reduce the attack surface. Security teams should also consider deploying network monitoring tools to detect anomalous traffic patterns that might indicate exploitation attempts, particularly focusing on unusual POST requests to the cstecgi.cgi endpoint. Organizations should conduct comprehensive inventory assessments to identify all affected TOTOLINK T10 devices and establish remediation timelines, while also implementing vulnerability scanning processes to detect similar issues in other network equipment. The ATT&CK framework categorizes this vulnerability under T1059 for command and control through remote services, and T1071 for application layer protocols, making it a significant concern for enterprise security teams implementing threat hunting strategies.