CVE-2026-21871Public exploitNetwork attack vector

Browser code execution via unescaped history URL

Published Jan 8, 2026 · Updated Jan 8, 2026

DOM-based XSS in Zauberzeug NiceGUI 2.13.0 through 3.4.1 allows remote attackers to execute JavaScript through crafted URLs. ui.navigate.history.push() and replace() embed their URL argument into generated JavaScript without escaping the string context. Exploitation requires an application to forward attacker-controlled data to either helper and a victim to trigger the affected navigation action, enabling client-side data access or page modification.

CVSS severity6.1
Medium
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DOM-based XSS in Zauberzeug NiceGUI 2.13.0 through 3.4.1 allows remote attackers to execute JavaScript through crafted URLs. ui.navigate.history.push() and replace() embed their URL argument into generated JavaScript without escaping the string context. Exploitation requires an application to forward attacker-controlled data to either helper and a victim to trigger the affected navigation action, enabling client-side data access or page modification.

The record

CVE
CVE-2026-21871
Published
Jan 8, 2026
Updated
Jan 8, 2026
Vendor
Zauberzeug
Product
NiceGUI
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 2.13.0, < 3.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zauberzeug · NiceGUIversion=>= 2.13.0, < 3.5.0

Published CVSS scores

6.1GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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