What is the CVSS score of CVE-2026-25516?

CVE-2026-25516 has a CVSS 3.1 base score of 6.1 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. EPSS exploitation probability: 0.0%.

Which versions of Python are affected by CVE-2026-25516?

Organizations using NiceGUI should be aware of moderate risk from CVE-2026-25516, a cross-site scripting vulnerability rated CVSS 6.1.. A patch is available.

Is there a public PoC exploit available for CVE-2026-25516?

Yes, a public proof-of-concept exploit is available for CVE-2026-25516. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2026-25516?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Verify Content-Security-Policy and output encoding.

Python CVE-2026-25516

MEDIUM

Cross-site Scripting (XSS) (CWE-79)

2026-02-06 security-advisories@github.com

GHSA-v82v-c5x8-w282

XSS Python Nicegui Zauberzeug

6.1

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

6.1 MEDIUM

AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:54 vuln.today

PoC Detected

Feb 20, 2026 - 15:43 vuln.today

Public exploit code

Patch released

Feb 20, 2026 - 15:43 nvd

Patch available

CVE Published

Feb 06, 2026 - 22:16 nvd

MEDIUM 6.1

DescriptionGitHub Advisory

NiceGUI is a Python-based UI framework. The ui.markdown() component uses the markdown2 library to convert markdown content to HTML, which is then rendered via innerHTML. By default, markdown2 allows raw HTML to pass through unchanged. This means that if an application renders user-controlled content through ui.markdown(), an attacker can inject malicious HTML containing JavaScript event handlers. Unlike other NiceGUI components that render HTML (ui.html(), ui.chat_message(), ui.interactive_image()), the ui.markdown() component does not provide or require a sanitize parameter, leaving applications vulnerable to XSS attacks. This vulnerability is fixed in 3.7.0.

AnalysisAI

Cross-site scripting in NiceGUI's ui.markdown() component allows unauthenticated attackers to inject malicious HTML and JavaScript into applications that render user-controlled markdown content, as the component lacks built-in sanitization unlike other NiceGUI HTML rendering functions. Public exploit code exists for this vulnerability affecting NiceGUI versions before 3.7.0. Applications using ui.markdown() with untrusted input are vulnerable to session hijacking, credential theft, and other client-side attacks.

Technical ContextAI

Classified as CWE-79 (Cross-site Scripting (XSS)). Affects Nicegui. NiceGUI is a Python-based UI framework. The ui.markdown() component uses the markdown2 library to convert markdown content to HTML, which is then rendered via innerHTML. By default, markdown2 allows raw HTML to pass through unchanged. This means that if an application renders user-controlled content through ui.markdown(), an attacker can inject malicious HTML containing JavaScript event handlers. Unlike other NiceGUI components that render HTML (ui.html(), ui.chat_message(), ui.interactive_image

RemediationAI

A vendor patch is available — apply it immediately. Fixed in version 3.7.0.. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.