CVE-2026-27156Public exploitNetwork attack vector

Cross-site scripting via evaluated method names

Published Feb 24, 2026 · Updated Feb 24, 2026

Cross-site scripting in Zauberzeug NiceGUI before 3.8.0 allows remote attackers to execute JavaScript in a victim's browser. The JavaScript-side runMethod function evaluates an unknown method name, while two Python APIs interpolate names without JSON escaping. Exploitation requires an application to pass attacker-controlled input into an affected API and a victim to open the crafted URL; successful execution can expose browser tokens or alter the page.

CVSS severity6.1
Medium
EPSS probability0.16%
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 Zauberzeug NiceGUI before 3.8.0 allows remote attackers to execute JavaScript in a victim's browser. The JavaScript-side runMethod function evaluates an unknown method name, while two Python APIs interpolate names without JSON escaping. Exploitation requires an application to pass attacker-controlled input into an affected API and a victim to open the crafted URL; successful execution can expose browser tokens or alter the page.

The record

CVE
CVE-2026-27156
Published
Feb 24, 2026
Updated
Feb 24, 2026
Vendor
Zauberzeug
Product
NiceGUI
Classifications
CWE-79, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 24, 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=< 3.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Zauberzeug · NiceGUIversion=< 3.8.0

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 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')
T1204.001User Execution: Malicious Link

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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