Is CVE-2021-21788 actively exploited?

No active exploitation of CVE-2021-21788 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2021-21788 be exploited remotely?

No. CVE-2021-21788 requires local access to exploit.

What is the CVSS score of CVE-2021-21788?

CVE-2021-21788 has a CVSS score of 8.8 (HIGH).

HOME VULNERABILITIESCVE-2021-21788

HIGH

CVE-2021-21788

CWE-782Published: July 7, 2021· Updated: Jun 17, 2026

8.8

CVSS v3.1

Official Description

A privilege escalation vulnerability exists in the way IOBit Advanced SystemCare Ultimate 14.2.0.220 driver handles Privileged I/O write requests. During IOCTL 0x9c40a0dc, the first dword passed in the input buffer is the device port to write to and the word at offset 4 is the value to write via the OUT instruction. The OUT instruction can write one byte to the given I/O device port, potentially leading to escalated privileges of unprivileged users. A local attacker can send a malicious IRP to trigger this vulnerability.

NVD Source

Technical Analysis

CVE-2021-21788 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.8.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.