Is CVE-2026-21874 in the CISA KEV catalog?

No. CVE-2026-21874 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-21874?

CVE-2026-21874 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2026-21874?

CVE-2026-21874 has an EPSS score of 0.51% (40th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-21874?

Upgrade nicegui to 3.5.0 or later.

CVE & CISA-KEV Catalog

CVE-2026-21874

MEDIUM

5.3

CVSS v3

NVD

Description

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.

CWE-772

How to fix

Remediation Available

niceguiNVD

Affected:>= 2.10.0, < 3.5.0Fixed in:3.5.0CVE-2026-21874derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityLow

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Exploit Intelligence

0.51%probability of exploitation in 30 days

40thpercentile

Low risk: more likely to be exploited than 40% of all known CVEs.

References

Patch1

github.com

Exploit1

github.com

Release Notes1

github.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-01-15.