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Home / Threats / CVE-2026-21873

CVE-2026-21873 - Nicegui Plugin

CVE-2026-21873

Vulnerability CVE-2026-21873 PLUGIN nicegui HIGH

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.

CVE-2026-21873

HIGH CVSS 7.2 Published 2026-01-08 Updated 2026-01-15
AI Risk High (76/100) Active Exploit: No strong signal Published Exploit: Public exploit references found Priority: P2 Urgent
Severity Band HIGH
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Affected Components 1
Reference Links 2
AI Risk Engine High (76/100)
Exploitability Medium
Active Exploitation No strong signal
Published Exploit Status Public exploit references found

Threat Timeline

  1. 2026-01-08 CVE published and first recorded in the threat feed.
  2. 2026-01-15 Record updated with latest vulnerability metadata.
  3. 2026-04-09 AI technical context refreshed for mitigation and impact guidance.
  4. Now Monitoring for follow-up changes, linked references, and new related CVEs.

AI Context

Machine-generated threat intelligence

AI Updated 12 days ago

AI enriched 12 days ago (2026-04-09 08:08 UTC)

Technical Summary

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.

Potential Impact

Severity is HIGH (CVSS 7.2). Depending on deployment context, affected components may be exposed to unauthorized actions or data integrity risk.

Exploitability Assessment

Exploitability is assessed as Medium based on published exploit references.

Primary risk drivers: published exploit references

Mitigation Recommendations

Validate affected product versions, prioritize patching, and monitor references for vendor remediation guidance. If immediate patching is not possible, apply compensating controls and limit exposure of vulnerable surfaces.

Detection & Monitoring

Track authentication anomalies, unexpected file writes, and suspicious plugin API activity around affected components.

Business Impact Lens

Prioritize remediation where affected components process customer data, admin sessions, or Internet-exposed workflows.

Affected Products

Nicegui PLUGIN · nicegui Affected: >= 2.22.03.5.0, <= 2.22.03.5.0 Fixed version not specified
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