CVE-2021-21787
A privilege escalation vulnerability exists in the way IOBit Advanced SystemCare Ultimate 14.2.0...
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 0x9c40a0d8, the first dword passed in the input buffer is the device port to write to and the byte 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.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
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 0x9c40a0d8, the first dword passed in the input buffer is the device port to write to and the byte 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.
- Record
CVE-2021-21787- CVSS 3.0
- 8.8 High
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Weakness
- CWE-782
- Updated
- 2026-11-02
EUVDEUVD-2021-8959
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 0x9c40a0d8, the first dword passed in the input buffer is the device port to write to and the byte 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.
- Record
EUVD-2021-8959- CVSS 3.0
- 8.8 High
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-2894-2ggj-v24h
A privilege escalation vulnerability exists in the way IOBit Advanced SystemCare Ultimate 14.2.0...
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 0x9c40a0d8, the first dword passed in the input buffer is the device port to write to and the byte 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.
- Record
GHSA-2894-2ggj-v24h- CVSS 3.1
- 8.8 High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - Updated
- 2026-11-02
NVD
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 0x9c40a0d8, the first dword passed in the input buffer is the device port to write to and the byte 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.
- Record
CVE-2021-21787- CVSS 3.1
- 8.8 High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - CVSS 3.0
- 8.8 High
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H - CVSS 2.0
- 4.6 Medium
AV:L/AC:L/Au:N/C:P/I:P/A:P - Weakness
- CWE-782
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-21787 is a high vulnerability (CVSS 8.8) in Iobit Advanced Systemcare Ultimate, published July 7, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.34%, the 27th percentile. No source names a fixed version.