# CVE-2016-9942: Memory corruption in n/a

> A heap-based buffer overflow in LibVNCClient allows remote servers to cause a crash or execute arbitrary code via crafted Ultra type tile messages.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 31 Dec 2016
- **Updated:** 6 Aug 2024
- **Also known as:** ALPINE-CVE-2016-9942, DEBIAN-CVE-2016-9942, GHSA-wx7p-737c-9wqw, UBUNTU-CVE-2016-9942

## What is CVE-2016-9942?

CVE-2016-9942 is a critical memory corruption vulnerability in n/a, published on 31 Dec 2016. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Heap-based buffer overflow in ultra.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote servers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted FramebufferUpdate message with the Ultra type tile, such that the LZO payload decompressed length exceeds what is specified by the tile dimensions.

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2016-9942?

It affects 1 product.


Products: Libvncserver Project Libvncserver.

## How do I fix CVE-2016-9942?

Upgrade to a fixed version.

## Is CVE-2016-9942 being exploited?

There is no known exploitation of CVE-2016-9942 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2016-9941](https://insights.sbomify.com/CVE-2016-9941/): Memory corruption in n/a (critical 9.8)
- [CVE-2026-32853](https://insights.sbomify.com/CVE-2026-32853/): LibVNCServer UltraZip Encoding Heap Out-of-bounds Read (medium 6.9)
- [CVE-2026-32854](https://insights.sbomify.com/CVE-2026-32854/): LibVNCServer httpd proxy NULL Pointer Dereference (medium 6.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-9942 and fix it if it is affected.

What it is: CVE-2016-9942 is a critical memory corruption vulnerability in n/a, published on 31 Dec 2016. 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-2016-9942 in the wild and no public exploit code.

Affected product: n/a. 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-2016-9942/ (Markdown: https://insights.sbomify.com/CVE-2016-9942/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-9942
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-9942
- OSV: https://osv.dev/vulnerability/CVE-2016-9942

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-9942/
Summaries are generated and may contain mistakes; the official description above is the record.