HIGH

CVE-2021-40556

CVSS v3

8.8

HIGH

EPSS Score

1.6 %

exploit probability, as of 2026-10-19

CISA KEV

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Neither OSV.dev nor the vendor advisories we read list affected versions for CVE-2021-40556 yet.

Full record on NVD

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.

Technical details

Published: 2022-10-06

Frequently asked questions

What is CVE-2021-40556?

Is CVE-2021-40556 actively exploited?

Active exploitation of CVE-2021-40556 has not been confirmed. Its EPSS score was 1.6% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-40556?

CVE-2021-40556 has a CVSS v3 base score of 8.8 (HIGH severity).

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