# CVE-2021-33626: Memory corruption in n/a

> Attackers can corrupt SMRAM memory and execute arbitrary code via insufficient validation of SWSMI handler buffer pointers in System Management Mode firmware.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/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:** 1 Oct 2021
- **Updated:** 11 Aug 2026
- **Also known as:** GHSA-9g63-gv45-4242

## What is CVE-2021-33626?

CVE-2021-33626 is a high-severity memory corruption vulnerability in Insyde Insydeh2o, published on 1 Oct 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability exists in SMM (System Management Mode) branch that registers a SWSMI handler that does not sufficiently check or validate the allocated buffer pointer(QWORD values for CommBuffer). This can be used by an attacker to corrupt data in SMRAM memory and even lead to arbitrary code execution.

Weakness: CWE-829 (Inclusion of Functionality from Untrusted Control Sphere)

## Which versions are affected by CVE-2021-33626?

It affects 17 products.


Products: Insyde Insydeh2o, Siemens Ruggedcom Apr1808 Firmware, Siemens Simatic Field Pg M5 Firmware, Siemens Simatic Field Pg M6 Firmware, Siemens Simatic Ipc127e Firmware, Siemens Simatic Ipc227g Firmware, Siemens Simatic Ipc277g Firmware, Siemens Simatic Ipc327g Firmware, Siemens Simatic Ipc377g Firmware, Siemens Simatic Ipc427e Firmware, Siemens Simatic Ipc477e Firmware, Siemens Simatic Ipc477e Pro Firmware, Siemens Simatic Ipc627e Firmware, Siemens Simatic Ipc647e Firmware, Siemens Simatic Ipc677e Firmware, Siemens Simatic Ipc847e Firmware, Siemens Simatic Itp1000 Firmware.

## How do I fix CVE-2021-33626?

No fix has been published for CVE-2021-33626 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-33626 being exploited?

There is no known exploitation of CVE-2021-33626 in the wild and no public exploit code.

## Other vulnerabilities in Insyde Insydeh2o

- [CVE-2021-41842](https://insights.sbomify.com/CVE-2021-41842/): Missing authorization in n/a (critical 9.8)
- [CVE-2023-22612](https://insights.sbomify.com/CVE-2023-22612/): Memory corruption in n/a (high 8.8)
- [CVE-2023-22613](https://insights.sbomify.com/CVE-2023-22613/): Memory corruption in n/a (high 8.8)
- [CVE-2023-22614](https://insights.sbomify.com/CVE-2023-22614/): Memory corruption in n/a (high 8.8)
- [CVE-2023-22615](https://insights.sbomify.com/CVE-2023-22615/): Memory corruption in n/a (high 8.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-33626 and fix it if it is affected.

What it is: CVE-2021-33626 is a high-severity memory corruption vulnerability in Insyde Insydeh2o, published on 1 Oct 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-2021-33626 in the wild and no public exploit code.

Affected product: Insyde Insydeh2o. 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-2021-33626/ (Markdown: https://insights.sbomify.com/CVE-2021-33626/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-33626
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-33626
- OSV: https://osv.dev/vulnerability/CVE-2021-33626

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-33626/
Summaries are generated and may contain mistakes; the official description above is the record.