# CVE-2023-3255: Qemu: vnc: infinite loop in inflate_buffer() leads to denial of service

> A remote authenticated VNC client can trigger an infinite loop in QEMU's VNC server via crafted clipboard data, causing a denial of service.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Sep 2023
- **Updated:** 8 Nov 2025
- **Also known as:** AZL-28791, AZL-35169, BELL-CVE-2023-3255, DEBIAN-CVE-2023-3255, GHSA-p5xv-5g6h-qw33, OESA-2023-1785, OESA-2023-1786, OESA-2023-1787, UBUNTU-CVE-2023-3255, openSUSE-SU-2024:13082-1

## What is CVE-2023-3255?

CVE-2023-3255 is a medium-severity denial of service vulnerability in Fedoraproject Fedora, published on 13 Sep 2023. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A flaw was found in the QEMU built-in VNC server while processing ClientCutText messages. A wrong exit condition may lead to an infinite loop when inflating an attacker controlled zlib buffer in the `inflate_buffer` function. This could allow a remote authenticated client who is able to send a clipboard to the VNC server to trigger a denial of service.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2023-3255?

It affects 3 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `qemu` | openSUSE:Tumbleweed | All versions | 8.0.3-2.1 |

Products: Fedoraproject Fedora, Qemu Qemu, Redhat Enterprise Linux.

## How do I fix CVE-2023-3255?

Apply the vendor's patch.

## Is CVE-2023-3255 being exploited?

There is no known exploitation of CVE-2023-3255 in the wild and no public exploit code.

## Other vulnerabilities in Fedoraproject Fedora

- [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild)
- [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-3255 and fix it if it is affected.

What it is: CVE-2023-3255 is a medium-severity denial of service vulnerability in Fedoraproject Fedora, published on 13 Sep 2023. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-3255 in the wild and no public exploit code.

Affected product: Fedoraproject Fedora. 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-2023-3255/ (Markdown: https://insights.sbomify.com/CVE-2023-3255/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-3255
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-3255
- OSV: https://osv.dev/vulnerability/CVE-2023-3255

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-3255/
Summaries are generated and may contain mistakes; the official description above is the record.