# CVE-2025-40743: Auth bypass in SINUMERIK 828D PPU.4

> Attackers can bypass VNC authentication to gain unauthorized remote access to SINUMERIK CNC controllers, compromising system confidentiality, integrity, and availability.

- **Severity:** High 8.7 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 Aug 2025
- **Updated:** 13 Aug 2025
- **Also known as:** GHSA-mr3f-gmg7-3h9c

## What is CVE-2025-40743?

CVE-2025-40743 is a high-severity authentication bypass vulnerability in Siemens SINUMERIK 828D PPU.4, published on 12 Aug 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability has been identified in SINUMERIK 828D PPU.4 (All versions < V4.95 SP5), SINUMERIK 828D PPU.5 (All versions < V5.25 SP1), SINUMERIK 840D sl (All versions < V4.95 SP5), SINUMERIK MC (All versions < V1.25 SP1), SINUMERIK MC V1.15 (All versions < V1.15 SP5), SINUMERIK ONE (All versions < V6.25 SP1), SINUMERIK ONE V6.15 (All versions < V6.15 SP5). The affected application improperly validates authentication for its VNC access service, allowing access with insufficient password verification.
This could allow an attacker to gain unauthorized remote access and potentially compromise system confidentiality, integrity, or availability.

Weakness: CWE-288 (Authentication Bypass Using an Alternate Path or Channel)

## Which versions are affected by CVE-2025-40743?


## How do I fix CVE-2025-40743?

No fix has been published for CVE-2025-40743 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-40743 being exploited?

There is no known exploitation of CVE-2025-40743 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40743 and fix it if it is affected.

What it is: CVE-2025-40743 is a high-severity authentication bypass vulnerability in Siemens SINUMERIK 828D PPU.4, published on 12 Aug 2025. 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-2025-40743 in the wild and no public exploit code.

Affected product: Siemens SINUMERIK 828D PPU.4. 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-2025-40743/ (Markdown: https://insights.sbomify.com/CVE-2025-40743/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40743
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40743
- OSV: https://osv.dev/vulnerability/CVE-2025-40743

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From sbomify Insights: https://insights.sbomify.com/CVE-2025-40743/
Summaries are generated and may contain mistakes; the official description above is the record.