# CVE-2021-21787: Privilege escalation in Iobit

> An attacker can escalate privileges by exploiting a driver vulnerability that allows arbitrary I/O port writes via a specific IOCTL request.

- **Severity:** High 8.8 (`CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Jul 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-2894-2ggj-v24h

## What is CVE-2021-21787?

CVE-2021-21787 is a high-severity vulnerability in Iobit, published on 7 Jul 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### 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 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.

Weakness: CWE-782 (Exposed IOCTL with Insufficient Access Control)

## Which versions are affected by CVE-2021-21787?

It affects 1 product.


Products: Iobit Advanced Systemcare Ultimate.

## How do I fix CVE-2021-21787?

No fix has been published for CVE-2021-21787 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-21787 being exploited?

There is no known exploitation of CVE-2021-21787 in the wild and no public exploit code.

## Other vulnerabilities in Iobit

- [CVE-2021-21786](https://insights.sbomify.com/CVE-2021-21786/): Privilege escalation in Iobit (high 8.8)
- [CVE-2021-21788](https://insights.sbomify.com/CVE-2021-21788/): Privilege escalation in Iobit (high 8.8)
- [CVE-2021-21789](https://insights.sbomify.com/CVE-2021-21789/): Privilege escalation in Iobit (high 8.8)
- [CVE-2018-9040](https://insights.sbomify.com/CVE-2018-9040/): Denial of service in n/a (high 7.8)
- [CVE-2018-9041](https://insights.sbomify.com/CVE-2018-9041/): Denial of service in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-21787 and fix it if it is affected.

What it is: CVE-2021-21787 is a high-severity vulnerability in Iobit, published on 7 Jul 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-21787 in the wild and no public exploit code.

Affected product: Iobit. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-21787/ (Markdown: https://insights.sbomify.com/CVE-2021-21787/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-21787
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-21787
- OSV: https://osv.dev/vulnerability/CVE-2021-21787

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-21787/
Summaries are generated and may contain mistakes; the official description above is the record.