{"id":"CVE-2021-40556","aliases":["EUVD-2021-27731","GHSA-9v8q-97m7-4x6q"],"status":"published","title":"A stack overflow vulnerability exists in the httpd service in ASUS RT-AX56U Router Version 3.0.0...","description":"A stack overflow vulnerability exists in the httpd service in ASUS RT-AX56U Router Version 3.0.0.4.386.44266. This vulnerability is caused by the strcat function called by \"caupload\" input handle function allowing the user to enter 0xFFFF bytes into the stack. This vulnerability allows an attacker to execute commands remotely. The vulnerability requires authentication.","severity":{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-10","score":0.01633,"percentile":0.76477,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-787"],"published":"2022-10-06T00:00:00Z","modified":"2026-06-17T04:07:07Z","products":[{"vendor":"asus","product":"rt-ax56u_firmware"}],"references":[{"url":"https://www.asus.com/tw/Networking-IoT-Servers/WiFi-Routers/ASUS-WiFi-Routers/RT-AX56U/HelpDesk_BIOS/","tags":["x_transferred","Product","Vendor Advisory"]},{"url":"https://x1ng.top/2021/10/14/ASUS%E6%A0%88%E6%BA%A2%E5%87%BA%E6%BC%8F%E6%B4%9E%E5%88%86%E6%9E%90/","tags":["x_transferred","Exploit","Third Party Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-40556"},{"url":"https://github.com/advisories/GHSA-9v8q-97m7-4x6q"}],"sources":{"cve":[{"id":"CVE-2021-40556","description":"A stack overflow vulnerability exists in the httpd service in ASUS RT-AX56U Router Version 3.0.0.4.386.44266. This vulnerability is caused by the strcat function called by \"caupload\" input handle function allowing the user to enter 0xFFFF bytes into the stack. This vulnerability allows an attacker to execute commands remotely. The vulnerability requires authentication.","status":"published","published":"2022-10-06T00:00:00Z","modified":"2024-08-04T02:44:10.797Z","updated_at":"2026-11-02T14:33:01.495293Z"}],"euvd":[{"id":"EUVD-2021-27731","description":"A stack overflow vulnerability exists in the httpd service in ASUS RT-AX56U Router Version 3.0.0.4.386.44266. This vulnerability is caused by the strcat function called by \"caupload\" input handle function allowing the user to enter 0xFFFF bytes into the stack. This vulnerability allows an attacker to execute commands remotely. The vulnerability requires authentication.","status":"published","published":"2022-10-06T00:00:00Z","modified":"2024-08-04T02:44:10Z","updated_at":"2026-11-03T03:24:20.264881Z"}],"ghsa":[{"id":"GHSA-9v8q-97m7-4x6q","title":"A stack overflow vulnerability exists in the httpd service in ASUS RT-AX56U Router Version 3.0.0...","description":"A stack overflow vulnerability exists in the httpd service in ASUS RT-AX56U Router Version 3.0.0.4.386.44266. This vulnerability is caused by the strcat function called by \"caupload\" input handle function allowing the user to enter 0xFFFF bytes into the stack. This vulnerability allows an attacker to execute commands remotely. The vulnerability requires authentication.","status":"published","published":"2022-10-06T18:52:02Z","modified":"2023-01-29T05:00:51Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T14:44:41.183486Z"}],"nvd":[{"id":"CVE-2021-40556","description":"A stack overflow vulnerability exists in the httpd service in ASUS RT-AX56U Router Version 3.0.0.4.386.44266. This vulnerability is caused by the strcat function called by \"caupload\" input handle function allowing the user to enter 0xFFFF bytes into the stack. This vulnerability allows an attacker to execute commands remotely. The vulnerability requires authentication.","status":"published","published":"2022-10-06T18:15:50.453Z","modified":"2026-06-17T04:07:07.53Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"primary"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T14:07:06.906968Z"}]}}