# CVE-2026-44041: UltraVNC vncWc2Mb calls wcslen() before validating that the wide string is NUL-terminated

> An out-of-bounds read in UltraVNC's string conversion helper can leak memory or crash the application if a non-terminated wide string is processed.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Jul 2026
- **Updated:** 9 Jul 2026
- **Also known as:** GHSA-f9fh-23qv-g394

## What is CVE-2026-44041?

CVE-2026-44041 is a medium-severity memory corruption vulnerability in uvnc UltraVNC, published on 1 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

UltraVNC through 1.8.2.2 contains an out-of-bounds read in the wide-string to multibyte conversion helper. In rfb/dh.cpp:204, the vncWc2Mb() function passes a caller-supplied WCHAR pointer to wcslen() before any bounds check. If the caller provides a wide-character buffer that is not properly NUL-terminated, wcslen() reads past the end of the buffer until it encounters a NUL wchar, resulting in an out-of-bounds read. Under typical Win32 API usage this requires an abnormal caller contract. Impact is limited to a potential information disclosure from adjacent memory regions or a process crash (denial of service) if the over-read crosses a page boundary.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-44041?

It affects 1 product.


Products: Uvnc Ultravnc.

## How do I fix CVE-2026-44041?

No fix has been published for CVE-2026-44041 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-44041 being exploited?

There is no known exploitation of CVE-2026-44041 in the wild and no public exploit code.

## Other vulnerabilities in uvnc UltraVNC

- [CVE-2019-8264](https://insights.sbomify.com/CVE-2019-8264/): Memory corruption in UltraVNC (critical 9.8)
- [CVE-2019-8265](https://insights.sbomify.com/CVE-2019-8265/): Memory corruption in UltraVNC (critical 9.8)
- [CVE-2019-8266](https://insights.sbomify.com/CVE-2019-8266/): Memory corruption in UltraVNC (critical 9.8)
- [CVE-2019-8280](https://insights.sbomify.com/CVE-2019-8280/): Memory corruption in UltraVNC (critical 9.8)
- [CVE-2018-15361](https://insights.sbomify.com/CVE-2018-15361/): Memory corruption in UltraVNC (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-44041 and fix it if it is affected.

What it is: CVE-2026-44041 is a medium-severity memory corruption vulnerability in uvnc UltraVNC, published on 1 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-44041 in the wild and no public exploit code.

Affected product: uvnc UltraVNC. 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-2026-44041/ (Markdown: https://insights.sbomify.com/CVE-2026-44041/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44041
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44041
- OSV: https://osv.dev/vulnerability/CVE-2026-44041

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-44041/
Summaries are generated and may contain mistakes; the official description above is the record.