ZDF
Sign inSign up

Vulnerabilities

Security incident · CVE-2026-21871

NiceGUI is a Python-based UI framework.

Published Jan 8, 2026 · catalog updated Jan 8, 2026 · NiceGUI is a Python-based

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-21871. EPSS is 0.27%. Act only if a listed version of NiceGUI is a Python-based is installed.

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 vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Medium6.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.27%
Remediation
Version ranges on file
Affected products
vendor zauberzeug nicegui 2.13.0, < 3.5.0

NiceGUI is a Python-based UI framework. From versions 2.13.0 to 3.4.1, there is a XSS risk in NiceGUI when developers pass attacker-controlled strings into ui.navigate.history.push() or ui.navigate.history.replace(). These helpers are documented as History API wrappers for updating the browser URL without page reload. However, if the URL argument is embedded into generated JavaScript without proper escaping, a crafted payload can break out of the intended string context and execute arbitrary JavaScript in the victim’s browser. Applications that do not pass untrusted input into ui.navigate.hist

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.

  • vendor zauberzeug nicegui 2.13.0, < 3.5.02.13.0, < 3.5.0

How to fix CVE-2026-21871

What to do

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

Should you patch?

No confirmed exploitation is on record for CVE-2026-21871. EPSS is 0.27%. Act only if a listed version of NiceGUI is a Python-based is installed.

Which versions are affected?

Compare what you have installed with zauberzeug nicegui 2.13.0, < 3.5.0 2.13.0, < 3.5.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.27%. 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. Jan 8, 2026 · EUVD

    Detected

    NiceGUI is a Python-based UI framework. From versions 2.13.0 to 3.4.1, there is a XSS risk in NiceGUI when developers pass attacker-controlled strings into ui.navigate.history.push() or ui.navigate.history.replace(). These helpers are documented as History API wrappers for updating the browser URL without page reload. However, if the URL argument is embedded into generated JavaScript without prope

  2. Jan 8, 2026 · EUVD

    Updated

    NiceGUI is a Python-based UI framework. From versions 2.13.0 to 3.4.1, there is a XSS risk in NiceGUI when developers pass attacker-controlled strings into ui.navigate.history.push() or ui.navigate.history.replace(). These helpers are documented as History API wrappers for updating the browser URL without page reload. However, if the URL argument is embedded into generated JavaScript without prope

Sources

  • CVE.orgVulnerability recordCVE-2026-21871

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-21871

    30-day exploitation probability 0.27%

    first.org
  • EUVDVulnerability recordEUVD-2026-1478

    NiceGUI is a Python-based UI framework. From versions 2.13.0 to 3.4.1, there is a XSS risk in NiceGUI when developers pass attacker-controlled strings into ui.navigate.history.push() or ui.navigate.history.replace(). These helpers are documented as History API wrappers for updati

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 6, 2026
  • CVE.orgOct 31, 2026
  • EUVDOct 30, 2026