CVE-2026-21874 json
NiceGUI has Redis connection leak via tab storage causes service degradation
published 10mo ago modified 4mo ago also EUVD-2026-1474 , GHSA-mp55-g7pj-rvm2 , PYSEC-2026-1703
- cvss
- 5.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.6%
- EPSS 0.6% chance of exploitation in 30 days, percentile 46%
- public exploits
- 0
- none known
Summary
NiceGUI is a Python-based UI framework. From versions v2.10.0 to 3.4.1, an unauthenticated attacker can exhaust Redis connections by repeatedly opening and closing browser tabs on any NiceGUI application using Redis-backed storage. Connections are never released, leading to service degradation when Redis hits its connection limit. NiceGUI continues accepting new connections - errors are logged but the app stays up with broken storage functionality. This issue has been patched in version 3.5.0.
Patch / fix
- pypi nicegui 3.5.0
- zauberzeug nicegui 3.5.0
Is CVE-2026-21874 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
- yes
- Technical impact
- partial
- Assessed
- 10mo ago
Exploit prediction
0.55% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-09).
Exploits and checks
- github.com https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mp55-g7pj-rvm2 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| GitHub | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| OSV | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | nicegui | >=2.10.0, <3.5.0 |
3.5.0 |
Affected products
- zauberzeug nicegui
Classification
- Weakness
-
- CWE-772 Missing Release of Resource after Effective Lifetime
References
-
github.com
/zauberzeug/nicegui/commit/6c52eb2c90c4b67387c025b29646b4bc1578eb83
web, patch
-
github.com
/zauberzeug/nicegui/security/advisories/GHSA-mp55-g7pj-rvm2
exploit, web, vendor-advisory
-
github.com
/zauberzeug/nicegui/releases/tag/v3.5.0
web, release-notes
-
nvd.nist.gov
/vuln/detail/CVE-2026-21874
advisory
-
github.com
/zauberzeug/nicegui
package
-
pypi.org
/project/nicegui
package
-
github.com
/advisories/GHSA-mp55-g7pj-rvm2
advisory
Sources
- CVE List CVE-2026-21874
- GitHub Advisory GHSA-mp55-g7pj-rvm2
- NVD CVE-2026-21874
- OSV PYSEC-2026-1703
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.