What’s Vulnerable › Vulnerabilities

CVE-2026-21874: NiceGUI has Redis connection leak via tab storage causes service degradation

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-01-08 · updated 2026-06-17
• Weakness: CWE-772

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.

Affected products

• zauberzeug nicegui: from 2.10.0 before 3.5.0 — fixed in 3.5.0

How to fix

Upgrade to a fixed version: zauberzeug nicegui 3.5.0. Check the vendor advisory for mitigations.

References

• https://github.com/zauberzeug/nicegui/commit/6c52eb2c90c4b67387c025b29646b4bc1578eb83
• https://github.com/zauberzeug/nicegui/releases/tag/v3.5.0
• https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mp55-g7pj-rvm2
• https://github.com/zauberzeug/nicegui/security/advisories/GHSA-mp55-g7pj-rvm2

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