# CVE-2026-33332: NiceGUI's unvalidated chunk size parameter in media routes can cause memory exhaustion

> Attackers can cause denial of service by forcing the server to load entire files into memory via unvalidated chunk size parameters in NiceGUI media routes.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Mar 2026
- **Updated:** 25 Mar 2026
- **Also known as:** GHSA-w5g8-5849-vj76, PYSEC-2026-2233

## What is CVE-2026-33332?

CVE-2026-33332 is a medium-severity denial of service vulnerability in zauberzeug nicegui, published on 24 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

NiceGUI is a Python-based UI framework. Prior to version 3.9.0, NiceGUI's app.add_media_file() and app.add_media_files() media routes accept a user-controlled query parameter that influences how files are read during streaming. The parameter is passed to the range-response implementation without validation, allowing an attacker to bypass chunked streaming and force the server to load entire files into memory at once. With large media files and concurrent requests, this can lead to excessive memory consumption, degraded performance, or denial of service. This issue has been patched in version 3.9.0.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-33332?

3 open source packages ship an affected version, including nicegui. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nicegui` | PyPI | All versions | 3.9.0 |
| `nicegui` | PyPI | All versions | 3.9.0 |
| `nicegui` | PyPI | All versions | 3.9.0 |

Products: Zauberzeug Nicegui.

## How do I fix CVE-2026-33332?

Upgrade nicegui to 3.9.0 or later.

## Is CVE-2026-33332 being exploited?

There is no known exploitation of CVE-2026-33332 in the wild and no public exploit code.

## Other vulnerabilities in zauberzeug nicegui

- [CVE-2026-25732](https://insights.sbomify.com/CVE-2026-25732/): NiceGUI's Path Traversal via Unsanitized FileUpload.name Enables Arbitrary File Write (high 7.5)
- [CVE-2025-66645](https://insights.sbomify.com/CVE-2025-66645/): NiceGUI Path Traversal Vulnerability in app.add_media_files() Allows Arbitrary File Reading (high 7.5)
- [CVE-2026-21873](https://insights.sbomify.com/CVE-2026-21873/): Zero-click XSS in all NiceGUI apps which uses `ui.sub_pages` (high 7.2)
- [CVE-2026-27156](https://insights.sbomify.com/CVE-2026-27156/): NiceGUI has XSS via Code Injection (medium 6.1)
- [CVE-2026-25516](https://insights.sbomify.com/CVE-2026-25516/): NiceGUI's XSS vulnerability in ui.markdown() allows arbitrary JavaScript execution through unsanitized HTML content (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33332 and fix it if it is affected.

What it is: CVE-2026-33332 is a medium-severity denial of service vulnerability in zauberzeug nicegui, published on 24 Mar 2026. 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-2026-33332 in the wild and no public exploit code.

Affected packages and fixed versions:
- nicegui (PyPI): affected all versions; fixed in 3.9.0
- nicegui (PyPI): affected all versions; fixed in 3.9.0
- nicegui (PyPI): affected all versions; fixed in 3.9.0

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-2026-33332/ (Markdown: https://insights.sbomify.com/CVE-2026-33332/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33332
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33332
- OSV: https://osv.dev/vulnerability/CVE-2026-33332

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33332/
Summaries are generated and may contain mistakes; the official description above is the record.