# CVE-2021-25662: Denial of service in SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants)

> A flaw in the SmartVNC client allows a remote attacker to cause a denial-of-service condition by sending a modified packet, affecting Siemens HMI panels and WinCC Runtime.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 May 2021
- **Updated:** 2 Jun 2026
- **Also known as:** GHSA-444h-8mr2-wm66

## What is CVE-2021-25662?

CVE-2021-25662 is a high-severity denial of service vulnerability in Siemens SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants), published on 12 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability has been identified in SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants) (All versions < V15.1 Update 6), SIMATIC HMI Comfort Outdoor Panels V16 7\" & 15\" (incl. SIPLUS variants) (All versions < V16 Update 4), SIMATIC HMI Comfort Panels V15 4\" - 22\" (incl. SIPLUS variants) (All versions < V15.1 Update 6), SIMATIC HMI Comfort Panels V16 4\" - 22\" (incl. SIPLUS variants) (All versions < V16 Update 4), SIMATIC HMI KTP Mobile Panels V15 KTP400F, KTP700, KTP700F, KTP900 and KTP900F (All versions < V15.1 Update 6), SIMATIC HMI KTP Mobile Panels V16 KTP400F, KTP700, KTP700F, KTP900 and KTP900F (All versions < V16 Update 4), SIMATIC WinCC Runtime Advanced V15 (All versions < V15.1 Update 6), SIMATIC WinCC Runtime Advanced V16 (All versions < V16 Update 4). SmartVNC client fails to handle an exception properly if the program execution process is modified after sending a packet from the server, which could result in a Denial-of-Service condition.

Weakness: CWE-755 (Improper Handling of Exceptional Conditions)

## Which versions are affected by CVE-2021-25662?

It affects 10 products.


Products: Siemens Simatic Hmi Comfort Outdoor Panels 15\" Firmware, Siemens Simatic Hmi Comfort Outdoor Panels 7\" Firmware, Siemens Simatic Hmi Comfort Panels 22\" Firmware, Siemens Simatic Hmi Comfort Panels 4\" Firmware, Siemens Simatic Hmi Ktp Mobile Panels Ktp400f Firmware, Siemens Simatic Hmi Ktp Mobile Panels Ktp700 Firmware, Siemens Simatic Hmi Ktp Mobile Panels Ktp700f Firmware, Siemens Simatic Hmi Ktp Mobile Panels Ktp900 Firmware, Siemens Simatic Hmi Ktp Mobile Panels Ktp900f Firmware, Siemens Simatic Wincc Runtime Advanced.

## How do I fix CVE-2021-25662?

No fix has been published for CVE-2021-25662 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-25662 being exploited?

There is no known exploitation of CVE-2021-25662 in the wild and no public exploit code.

## Other vulnerabilities in Siemens SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants)

- [CVE-2021-27384](https://insights.sbomify.com/CVE-2021-27384/): Memory corruption in SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants) (critical 9.8)
- [CVE-2021-25660](https://insights.sbomify.com/CVE-2021-25660/): Memory corruption in SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants) (high 7.5)
- [CVE-2021-25661](https://insights.sbomify.com/CVE-2021-25661/): Memory corruption in SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants) (high 7.5)
- [CVE-2021-27383](https://insights.sbomify.com/CVE-2021-27383/): Denial of service in SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants) (high 7.5)
- [CVE-2021-27385](https://insights.sbomify.com/CVE-2021-27385/): Denial of service in SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants) (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-25662 and fix it if it is affected.

What it is: CVE-2021-25662 is a high-severity denial of service vulnerability in Siemens SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants), published on 12 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-25662 in the wild and no public exploit code.

Affected product: Siemens SIMATIC HMI Comfort Outdoor Panels V15 7\" & 15\" (incl. SIPLUS variants). 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-2021-25662/ (Markdown: https://insights.sbomify.com/CVE-2021-25662/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-25662
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-25662
- OSV: https://osv.dev/vulnerability/CVE-2021-25662

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-25662/
Summaries are generated and may contain mistakes; the official description above is the record.