CVE-2026-33332

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.

Affected applications: NiceGUI applications that serve media content via app.add_media_file() or app.add_media_files(), particularly those serving large files (video, audio).

What an attacker can do:

• Force the server to load entire files into memory instead of streaming them in chunks
• Amplify memory usage with concurrent requests to large media files
• Cause performance degradation, memory pressure, and potential OOM conditions

Attack difficulty: Low - requires only a crafted query parameter.

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2026-33332 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.9.0); upgrading removes the vulnerable code path.

Kodem intelligence

Upgrade to a patched version of NiceGUI.

As a workaround, restrict access to media endpoints or strip unexpected query parameters at a reverse proxy layer.

1. What is CVE-2026-33332? CVE-2026-33332 is a medium-severity improper input validation vulnerability in nicegui (pip), affecting versions <= 3.8.0. It is fixed in 3.9.0. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
2. How severe is CVE-2026-33332? CVE-2026-33332 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of nicegui are affected by CVE-2026-33332? nicegui (pip) versions <= 3.8.0 is affected.
4. Is there a fix for CVE-2026-33332? Yes. CVE-2026-33332 is fixed in 3.9.0. Upgrade to this version or later.
5. Is CVE-2026-33332 exploitable, and should I be worried? Whether CVE-2026-33332 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-33332 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-33332? Upgrade nicegui to 3.9.0 or later.