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Vulnerabilities

Security fix · CVE-2025-66469

NiceGUI is a Python-based UI framework.

Published Dec 9, 2025 · catalog updated Oct 19, 2026 · NiceGUI is a Python-based

Open the advisory

Exploitation likelihood is not on this record for CVE-2025-66469. A missing EPSS score is not a low risk. Compare NiceGUI is a Python-based with the linked advisory before you change production.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (NiceGUI is a Python-based).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
  • EPSS is missing. A missing score is not a low risk.
Severity
Medium6.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
Awaiting synchronization with FIRST
Remediation
Advisory link
Affected products
cpe zauberzeug/nicegui

NiceGUI is a Python-based UI framework. Versions 3.3.1 and below are vulnerable to Reflected XSS through its ui.add_css, ui.add_scss, and ui.add_sass functions. The functions lack proper sanitization or encoding for the JavaScript context they generate. An attacker can break out of the intended or tags by injecting closing tags (e.g., or ), allowing for the execution of arbitrary JavaScript. This issue is fixed in version 3.4.0.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe zauberzeug/niceguiversion unspecified

How to fix CVE-2025-66469

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

Exploitation likelihood is not on this record for CVE-2025-66469. A missing EPSS score is not a low risk. Compare NiceGUI is a Python-based with the linked advisory before you change production.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-79: Cross-site Scripting (XSS). EPSS is not on this record yet. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Dec 9, 2025 · NIST NVD

    Detected

    NiceGUI is a Python-based UI framework. Versions 3.3.1 and below are vulnerable to Reflected XSS through its ui.add_css, ui.add_scss, and ui.add_sass functions. The functions lack proper sanitization or encoding for the JavaScript context they generate. An attacker can break out of the intended or tags by injecting closing tags (e.g., or ), allowing for the execution of arbitrary JavaScript. This

  2. Oct 19, 2026 · NIST NVD

    Updated

    NiceGUI is a Python-based UI framework. Versions 3.3.1 and below are vulnerable to Reflected XSS through its ui.add_css, ui.add_scss, and ui.add_sass functions. The functions lack proper sanitization or encoding for the JavaScript context they generate. An attacker can break out of the intended or tags by injecting closing tags (e.g., or ), allowing for the execution of arbitrary JavaScript. This

Sources

  • CVE.orgVulnerability recordCVE-2025-66469

    Official CVE identifier

    cve.org
  • NIST NVDVulnerability recordCVE-2025-66469

    NiceGUI is a Python-based UI framework. Versions 3.3.1 and below are vulnerable to Reflected XSS through its ui.add_css, ui.add_scss, and ui.add_sass functions. The functions lack proper sanitization or encoding for the JavaScript context they generate. An attacker can break out

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 19, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.