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Vulnerability details: VCID-en8b-9bda-x7cb
Vulnerability ID VCID-en8b-9bda-x7cb
Aliases CVE-2026-21873
GHSA-mhpg-c27v-6mxr
Summary NiceGUI apps which use `ui.sub_pages` vulnerable to zero-click XSS 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_.
Status Published
Exploitability 0.5
Weighted Severity 8.0
Risk 4.0
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 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-21873
epss 9e-05 https://api.first.org/data/v1/epss?cve=CVE-2026-21873
cvssv3.1_qr HIGH https://github.com/advisories/GHSA-mhpg-c27v-6mxr
cvssv3.1 7.2 https://github.com/zauberzeug/nicegui
generic_textual HIGH https://github.com/zauberzeug/nicegui
cvssv3.1 7.2 https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
generic_textual HIGH https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
ssvc Track https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
cvssv3.1 7.2 https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mhpg-c27v-6mxr
cvssv3.1_qr HIGH https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mhpg-c27v-6mxr
generic_textual HIGH https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mhpg-c27v-6mxr
ssvc Track https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mhpg-c27v-6mxr
cvssv3.1 7.2 https://nvd.nist.gov/vuln/detail/CVE-2026-21873
generic_textual HIGH https://nvd.nist.gov/vuln/detail/CVE-2026-21873
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2026-21873
https://github.com/zauberzeug/nicegui
https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
CVE-2026-21873 https://nvd.nist.gov/vuln/detail/CVE-2026-21873
GHSA-mhpg-c27v-6mxr https://github.com/advisories/GHSA-mhpg-c27v-6mxr
GHSA-mhpg-c27v-6mxr https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mhpg-c27v-6mxr
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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:N/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:Y/T:P/P:M/B:A/M:M/D:T/2026-01-08T15:11:07Z/ Found at https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N Found at https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mhpg-c27v-6mxr
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:Y/T:P/P:M/B:A/M:M/D:T/2026-01-08T15:11:07Z/ Found at https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mhpg-c27v-6mxr
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2026-21873
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 0.05901
EPSS Score 0.0002
Published At June 5, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-06-02T04:49:25.758596+00:00 GitLab Importer Import https://gitlab.com/gitlab-org/advisories-community/-/blob/main/pypi/nicegui/CVE-2026-21873.yml 38.6.0