CVE-2026-82539
Received Received - Intake

Memory Corruption in TOTOLINK A720R via MAC Filtering

Publication date: 2026-08-30

Last updated on: 2026-08-30

Assigner: VulDB

Description
A vulnerability was determined in TOTOLINK A720R 4.1.5cu.630_B20250509. This impacts the function setMacFilterRules of the file cstecgi.cgi of the component MAC Filtering. Executing a manipulation of the argument desc can lead to memory corruption. The attack may be launched remotely. The exploit has been publicly disclosed and may be utilized.

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Meta Information

Published
2026-08-30
Last Modified
2026-08-30
Generated
2026-08-30
AI Q&A
2026-08-30
EPSS Evaluated
N/A
NVD
CVE-2026-82539
EUVD
EUVD-2026-68181

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
totolink a720r 4.1.5cu.630_b20250509

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-119 The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

Attack-Flow Graph

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Executive Summary

This vulnerability is a stack-based buffer overflow in TOTOLINK A720R routers running firmware version V4.1.5cu.630_B20250509. It affects the setMacFilterRules function in the cstecgi.cgi binary. An authenticated administrator can send a crafted request with an overly long desc parameter, which is copied into a fixed-size stack buffer without bounds checking. This allows overwriting the saved return address, enabling control flow hijacking.

Detection Guidance

To detect this vulnerability, check if your TOTOLINK A720R router is running firmware version V4.1.5cu.630_B20250509. Inspect network traffic for requests to the cstecgi.cgi binary with the setMacFilterRules handler and a long desc parameter. Use tools like Wireshark to monitor for malformed HTTP requests targeting this endpoint.

Impact Analysis

An attacker with network access and admin privileges can exploit this to execute arbitrary code on the device. This may lead to system compromise, allowing actions like rebooting the device, logging out sessions, clearing logs, or enabling unauthorized services like Telnet. The attacker could gain full control over the router's operations.

Compliance Impact

This vulnerability allows authenticated attackers to execute arbitrary code on the device, potentially leading to unauthorized access, data exfiltration, or manipulation. Such risks could violate GDPR's data protection requirements (e.g., Article 32) and HIPAA's security rules (e.g., integrity and confidentiality safeguards) if the device processes sensitive data.

Mitigation Strategies

Immediately update the TOTOLINK A720R router to the latest firmware version if an update is available. Disable remote administration access to the router if not required. Restrict network access to the router's web interface to trusted IP addresses only. Monitor logs for suspicious activity related to the cstecgi.cgi endpoint.

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