CVE-2026-21873 json
Zero-click XSS in all NiceGUI apps which uses `ui.sub_pages`
published 10mo ago modified 4mo ago also EUVD-2026-1475 , GHSA-mhpg-c27v-6mxr , PYSEC-2026-1702
- cvss
- 7.2
- 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 17%
- 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 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. This issue has been patched in version 3.5.0.
Patch / fix
- pypi nicegui 3.5.0
- zauberzeug nicegui 3.5.0
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Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 10mo ago
Exploit prediction
0.26% chance of exploitation in the next 30 days, higher than 17% of all scored CVEs (FIRST EPSS, 2026-11-09).
Exploits and checks
- github.com https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mhpg-c27v-6mxr referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N |
| GitHub | 3.1 | 7.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N |
| NVD | 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 | 7.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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-mhpg-c27v-6mxr
web, exploit, vendor-advisory
-
github.com
/zauberzeug/nicegui/releases/tag/v3.5.0
web, release-notes
-
nvd.nist.gov
/vuln/detail/CVE-2026-21873
advisory
-
github.com
/zauberzeug/nicegui
package
-
pypi.org
/project/nicegui
package
-
github.com
/advisories/GHSA-mhpg-c27v-6mxr
advisory
Sources
- CVE List CVE-2026-21873
- GitHub Advisory GHSA-mhpg-c27v-6mxr
- NVD CVE-2026-21873
- OSV PYSEC-2026-1702
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.