Overview
CVE-2025-60685 is a medium-severity stack buffer overflow vulnerability affecting ToToLink A720R routers running firmware version V4.1.5cu.614_B20230630. This flaw resides within the sysconf binary and allows a malicious actor with filesystem write privileges to potentially execute arbitrary code on the vulnerable device. This article provides a detailed analysis of the vulnerability, its potential impact, and recommended mitigation strategies.
Technical Details
The vulnerability stems from the sub_401EE0 function within the sysconf binary. The function reads the /proc/stat file using fgets() into a local buffer. Subsequently, it attempts to parse a line from this buffer using sscanf() and the %s format specifier, writing the parsed data into a single-byte variable. This is a clear buffer overflow condition. By crafting a malicious /proc/stat file containing a string longer than one byte, an attacker can overwrite adjacent stack memory.
The requirement for filesystem write access is crucial. An attacker would need to find a separate vulnerability or leverage existing misconfigurations to gain the necessary privileges to modify the contents of /proc/stat. However, once achieved, this vulnerability offers a direct path to arbitrary code execution.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) score for CVE-2025-60685 is 5.1 (Medium). The vector string is likely AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H. This reflects the local attack vector (AV:L), low attack complexity (AC:L), high privileges required (PR:H), no user interaction required (UI:N), unchanged security scope (S:U), and high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). The need for prior file system write access limits the exploitability compared to a fully remote vulnerability.
Possible Impact
Successful exploitation of CVE-2025-60685 can have severe consequences, including:
- Arbitrary Code Execution: An attacker can gain complete control over the affected ToToLink A720R router.
- Malware Installation: The router can be used as a staging ground for malware distribution or as part of a botnet.
- Data Theft: Sensitive information stored on or passing through the router can be compromised.
- Denial of Service: The router’s functionality can be disrupted, causing network outages.
Mitigation and Patch Steps
The recommended mitigation steps are:
- Apply Firmware Updates: Check the ToToLink official website for updated firmware that addresses this vulnerability. Install the latest version as soon as it becomes available.
- Restrict Access: Limit access to the router’s filesystem to only authorized users and processes. This may involve reviewing and hardening existing access controls.
- Monitor Router Activity: Implement monitoring solutions to detect suspicious activity on the router, such as unexpected file modifications.
