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Vulnerability details: VCID-ztch-92ab-gue7
Vulnerability ID VCID-ztch-92ab-gue7
Aliases CVE-2026-21871
GHSA-7grm-h62g-5m97
Summary NiceGUI is vulnerable to XSS via Unescaped URL in ui.navigate.history.push() / replace() XSS risk exists in NiceGUI when developers pass attacker-controlled strings into `ui.navigate.history.push()` or `ui.navigate.history.replace()`. These helpers are documented as History API wrappers for updating the browser URL without page reload. However, if the URL argument is embedded into generated JavaScript without proper escaping, a crafted payload can break out of the intended string context and execute arbitrary JavaScript in the victim’s browser. **Applications that do not pass untrusted input into `ui.navigate.history.push/replace` are not affected.**
Status Published
Exploitability 0.5
Weighted Severity 6.2
Risk 3.1
Affected and Fixed Packages Package Details
Weaknesses (3)
CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
epss 0.00021 https://api.first.org/data/v1/epss?cve=CVE-2026-21871
cvssv3.1_qr MODERATE https://github.com/advisories/GHSA-7grm-h62g-5m97
cvssv3.1 6.1 https://github.com/zauberzeug/nicegui
generic_textual MODERATE https://github.com/zauberzeug/nicegui
cvssv3.1 6.1 https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
generic_textual MODERATE https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
ssvc Track https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
cvssv3.1 6.1 https://github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97
cvssv3.1_qr MODERATE https://github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97
generic_textual MODERATE https://github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97
ssvc Track https://github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97
cvssv3.1 6.1 https://nvd.nist.gov/vuln/detail/CVE-2026-21871
generic_textual MODERATE https://nvd.nist.gov/vuln/detail/CVE-2026-21871
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2026-21871
https://github.com/zauberzeug/nicegui
https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
CVE-2026-21871 https://nvd.nist.gov/vuln/detail/CVE-2026-21871
GHSA-7grm-h62g-5m97 https://github.com/advisories/GHSA-7grm-h62g-5m97
GHSA-7grm-h62g-5m97 https://github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://github.com/zauberzeug/nicegui
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:P/A:N/T:P/P:M/B:A/M:M/D:T/2026-01-08T15:14:43Z/ Found at https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:P/A:N/T:P/P:M/B:A/M:M/D:T/2026-01-08T15:14:43Z/ Found at https://github.com/zauberzeug/nicegui/security/advisories/GHSA-7grm-h62g-5m97
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2026-21871
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.06132
EPSS Score 0.00021
Published At May 30, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-05-30T21:05:48.518067+00:00 GitLab Importer Import https://gitlab.com/gitlab-org/advisories-community/-/blob/main/pypi/nicegui/CVE-2026-21871.yml 38.6.0