CVE-2026-82539: Memory Corruption in TOTOLINK A720R

This vulnerability exists in TOTOLINK A720R firmware version 4.1.5cu.630_B20250509 within the setMacFilterRules function of the cstecgi.cgi file, which handles MAC filtering rules. Remote attackers can exploit improper handling of the desc argument to cause memory corruption, potentially leading to denial of service or code execution. The vulnerability is remotely exploitable without user interaction and requires high privileges. The CVSS 4.0 vector indicates network attack vector, low attack complexity, no privileges required, no user interaction, and high impact on confidentiality, integrity, availability, and security requirements. The vulnerability was publicly disclosed on 2026-08-30, but no official patch or mitigation has been documented.

Successful exploitation can lead to memory corruption, which may allow an attacker to disrupt device operation or execute arbitrary code remotely. The vulnerability affects confidentiality, integrity, availability, and security controls at a high level. Given the critical CVSS score of 9.4, the impact is severe on affected devices running the specified firmware version.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, users should limit network exposure of the affected device and consider disabling remote management features if possible. Monitor vendor communications for updates on patches or official mitigations.