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Vulnerabilities

Security fix · CVE-2026-21873

NiceGUI is a Python-based UI framework.

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

Last checked Oct 31, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-21873. EPSS is 0.26%. 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
High7.2
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.26%
Remediation
Version ranges on file
Affected products
vendor zauberzeug nicegui 2.22.0, < 3.5.0

NiceGUI is a Python-based UI framework. From versions 2.22.0 to 3.4.1, an unsafe implementation in the pushstate event listener used by ui.sub_pages allows an attacker to manipulate the fragment identifier of the URL, which they can do despite being cross-site, using an iframe. This issue has been patched in version 3.5.0.

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.

  • vendor zauberzeug nicegui 2.22.0, < 3.5.02.22.0, < 3.5.0

How to fix CVE-2026-21873

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-2026-21873. EPSS is 0.26%. 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 2.22.0, < 3.5.0 2.22.0, < 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 0.26%. 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 2.22.0 to 3.4.1, an unsafe implementation in the pushstate event listener used by ui.sub_pages allows an attacker to manipulate the fragment identifier of the URL, which they can do despite being cross-site, using an iframe. This issue has been patched in version 3.5.0.

  2. Jan 8, 2026 · EUVD

    Updated

    NiceGUI is a Python-based UI framework. From versions 2.22.0 to 3.4.1, an unsafe implementation in the pushstate event listener used by ui.sub_pages allows an attacker to manipulate the fragment identifier of the URL, which they can do despite being cross-site, using an iframe. This issue has been patched in version 3.5.0.

Sources

  • CVE.orgVulnerability recordCVE-2026-21873

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-21873

    30-day exploitation probability 0.26%

    first.org
  • EUVDVulnerability recordEUVD-2026-1475

    NiceGUI is a Python-based UI framework. From versions 2.22.0 to 3.4.1, an unsafe implementation in the pushstate event listener used by ui.sub_pages allows an attacker to manipulate the fragment identifier of the URL, which they can do despite being cross-site, using an iframe. T

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Oct 31, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSOct 31, 2026
  • CVE.orgOct 31, 2026
  • EUVDOct 30, 2026