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CVE-2026-21873

Zauberzeug Nicegui cross-site scripting (XSS)

7.2 HIGHPublic exploitEPSS 0.26%
  1. Published8 Jan 2026

Description

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeChanged
ConfidentialityLow
IntegrityLow
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

Affected products

Zauberzeug Nicegui≥ 2.22.0 < 3.5.0

Remediation

Fixed in
Zauberzeug Nicegui≥ 3.5.0

References

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Frequently asked

Is CVE-2026-21873 being actively exploited?

CVE-2026-21873 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.26%.

How severe is CVE-2026-21873?

CVE-2026-21873 has a CVSS 3.1 base score of 7.2, rated high. EPSS estimates a 0.26% probability of exploitation.

Which products are affected by CVE-2026-21873?

Affected products include Zauberzeug Nicegui.

How do I fix CVE-2026-21873?

Upgrade affected software to a fixed version, for example Zauberzeug Nicegui 3.5.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-21873 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.