CVE-2026-25516Public exploitNetwork attack vector

JavaScript execution via unsanitized Markdown HTML

Published Feb 6, 2026 · Updated Feb 6, 2026

Cross-site scripting in NiceGUI before 3.7.0 allows remote attackers to execute JavaScript through user-controlled ui.markdown content. The ui.markdown component passes markdown2 output containing raw HTML into browser innerHTML without sanitizing event-handler attributes. Exploitation requires an application to render attacker-controlled Markdown and a victim to load the affected page, enabling script execution in that user's browser context.

CVSS severity6.1
Medium
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in NiceGUI before 3.7.0 allows remote attackers to execute JavaScript through user-controlled ui.markdown content. The ui.markdown component passes markdown2 output containing raw HTML into browser innerHTML without sanitizing event-handler attributes. Exploitation requires an application to render attacker-controlled Markdown and a victim to load the affected page, enabling script execution in that user's browser context.

The record

CVE
CVE-2026-25516
Published
Feb 6, 2026
Updated
Feb 6, 2026
Vendor
Zauberzeug
Product
NiceGUI
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 6, 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=< 3.7.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zauberzeug · NiceGUIversion=< 3.7.0

Published CVSS scores

6.1GitHub, Inc.CVSS: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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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')
T1189Drive-by Compromise

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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