CVE-2026-21872 json
NiceGUI apps are vulnerable to XSS which uses `ui.sub_pages` and render arbitrary user-provided links
published 10mo ago modified 4mo ago also EUVD-2026-1477 , GHSA-m7j5-rq9j-6jj9 , PYSEC-2026-1701
- cvss
- 6.1
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 19%
- public exploits
- 0
- none known
Summary
NiceGUI is a Python-based UI framework. From versions 2.22.0 to 3.4.1, an unsafe implementation in the click event listener used by ui.sub_pages, combined with attacker-controlled link rendering on the page, causes XSS when the user actively clicks on the link. This issue has been patched in version 3.5.0.
Patch / fix
- pypi nicegui 3.5.0
- zauberzeug nicegui 3.5.0
Is CVE-2026-21872 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- partial
- Assessed
- 10mo ago
Exploit prediction
0.27% chance of exploitation in the next 30 days, higher than 19% of all scored CVEs (FIRST EPSS, 2026-11-09).
Exploits and checks
- github.com https://github.com/zauberzeug/nicegui/security/advisories/GHSA-m7j5-rq9j-6jj9 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
| GitHub | 3.1 | 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
| OSV | 3.1 | 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | nicegui | >=2.22.0, <3.5.0 |
3.5.0 |
Affected products
- zauberzeug nicegui
Classification
- Weakness
-
- CWE-79 Improper Neutralization of Input During Web Page Generation
References
-
github.com
/zauberzeug/nicegui/security/advisories/GHSA-m7j5-rq9j-6jj9
web, exploit, vendor-advisory
-
github.com
/zauberzeug/nicegui/releases/tag/v3.5.0
web, release-notes
-
nvd.nist.gov
/vuln/detail/CVE-2026-21872
advisory
-
github.com
/zauberzeug/nicegui
package
-
pypi.org
/project/nicegui
package
-
github.com
/advisories/GHSA-m7j5-rq9j-6jj9
advisory
Sources
- CVE List CVE-2026-21872
- GitHub Advisory GHSA-m7j5-rq9j-6jj9
- NVD CVE-2026-21872
- OSV PYSEC-2026-1701
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.