CVE-2025-28136 in A800R
Summary
by MITRE • 04/15/2025
TOTOLINK A800R V4.1.2cu.5137_B20200730 was found to contain a buffer overflow vulnerability in the downloadFile.cgi.
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Analysis
by VulDB Data Team • 05/24/2025
The vulnerability identified as CVE-2025-28136 represents a critical buffer overflow flaw within the TOTOLINK A800R router firmware version V4.1.2cu.5137_B20200730. This issue specifically resides in the downloadFile.cgi component, which serves as a web interface handler for file download operations. The affected device operates under the assumption that incoming data from network requests will not exceed predetermined buffer limits, creating a scenario where maliciously crafted input can overwrite adjacent memory regions. Such vulnerabilities typically arise from insufficient input validation mechanisms that fail to properly check the length of data before copying it into fixed-size memory buffers. The presence of this flaw in a networking device with web-based administrative capabilities significantly expands the attack surface and potential exploitation vectors.
The technical implementation of this buffer overflow vulnerability stems from improper bounds checking within the downloadFile.cgi script. When the router processes file download requests through its web interface, it likely employs a fixed-length buffer to store incoming filename or path parameters without adequate validation of input size. This allows an attacker to submit carefully constructed payloads that exceed the allocated buffer space, causing memory corruption that can lead to arbitrary code execution. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and may also exhibit characteristics of CWE-787, representing out-of-bounds write vulnerabilities. Attackers could leverage this weakness to execute malicious code on the affected device, potentially gaining unauthorized administrative access or disrupting network operations.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can enable full system compromise of the affected router. Given that the TOTOLINK A800R serves as a central networking device within home and small office environments, successful exploitation could provide attackers with persistent access to local networks, enabling man-in-the-middle attacks, DNS hijacking, or redirection of network traffic. The vulnerability's web-based nature means that exploitation could occur remotely without requiring physical access to the device, making it particularly dangerous for widespread deployment. Additionally, the compromised device could serve as a pivot point for further attacks within the network, potentially allowing attackers to escalate privileges and access sensitive network resources. According to ATT&CK framework, this vulnerability maps to T1059.007 for command and scripting interpreter and T1071.001 for application layer protocol, as attackers could leverage the compromised device for lateral movement and command execution.
Mitigation strategies for CVE-2025-28136 should prioritize immediate firmware updates from TOTOLINK, as the vendor likely has patched the vulnerable code. Network administrators should implement network segmentation to limit the potential impact of exploitation, while monitoring for suspicious network traffic patterns that may indicate exploitation attempts. Access controls should be strengthened through secure configuration of the router's web interface, including disabling unnecessary services and implementing strong authentication mechanisms. Network-based intrusion detection systems can help identify malformed requests targeting the vulnerable downloadFile.cgi endpoint, while regular security assessments should verify that the updated firmware properly addresses the buffer overflow condition. Organizations should also consider implementing network access controls to restrict administrative access to critical network infrastructure, reducing the attack surface for such vulnerabilities. The vulnerability demonstrates the importance of maintaining up-to-date firmware and implementing defense-in-depth strategies to protect network infrastructure from exploitation attempts targeting embedded systems.