VulnerabilityPublished 8 Jan 2026

CVE-2026-21874: zauberzeug nicegui · Missing Release of Resource after Effective Lifetime

Affects zauberzeug niceguiSource CVE Database V5

Not known to be exploited · CVSS 5.3 Medium : upgrade to 3.5.0 when convenient.

Data as of 26 Oct 2026, 10:12 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.5% chance of exploitation in 30 days – higher than 45% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.5.0, 3.0.0

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 8 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade nicegui to 3.5.0; nicegui to 3.0.0.

Affected software

Product	Affected	Fixed in
zauberzeugnicegui	Affected >=2.10.0 <3.5.0	Fixed in 3.5.0
PyPInicegui`pkg:pypi/nicegui`Other threats	Affected >=2.10.0 <3.0.0	Fixed in 3.0.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately upgrade NiceGUI to version 3.5.0 or later, where the vulnerability is patched. Until upgrading is possible, implement monitoring on Redis connection counts and set alerts for abnormal connection usage patterns. Configure Redis to limit maximum connections per client or implement connection pooling to mitigate exhaustion risks. Employ web application firewalls or rate limiting to restrict rapid tab opening/closing behaviors from single IP addresses. Consider isolating Redis instances used by NiceGUI applications to prevent broader impact on other services. Regularly audit application dependencies and maintain an inventory of NiceGUI versions in use. Finally, educate developers and administrators about proper resource management and encourage timely patching of third-party components.

Description

CVE-2026-21874 is a medium-severity vulnerability in the NiceGUI Python UI framework versions 2.10.0 through 3.4.1. It allows unauthenticated attackers to exhaust Redis connections by repeatedly opening and closing browser tabs on applications using Redis-backed storage. The vulnerability arises because Redis connections are not properly released, leading to service degradation when the Redis connection limit is reached. Although the NiceGUI app remains operational, storage functionality breaks and errors are logged. This issue does not impact confidentiality or integrity but affects availability. The vulnerability has been patched in version 3.

Impact

For European organizations, this vulnerability primarily threatens the availability of applications built with NiceGUI that rely on Redis-backed storage. Service degradation or partial denial of service can disrupt business operations, especially for customer-facing or internal applications critical to workflows. Organizations using affected versions risk operational interruptions if attackers or even inadvertent user behavior triggers connection exhaustion. While confidentiality and data integrity are not directly impacted, the loss of storage functionality can lead to data loss or inconsistent application states. The impact is more pronounced for organizations with high traffic web applications or those that cannot quickly patch or restart Redis services. Additionally, sectors with stringent uptime requirements, such as finance, healthcare, and public services, may face compliance and reputational risks due to service unavailability.

CWE-772Missing Release of Resource after Effective Lifetime (opens in a new tab)
Base weaknessLikelihood of exploit: High
The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation
It is good practice to be responsible for freeing all resources you allocate and to be consistent with how and where you free resources in a function. If you allocate resources that you intend to free upon completion of the function, you must be sure to free the resources at all exit points for that function including…
Operation · Architecture and Design · Resource Limitation
Use resource-limiting settings provided by the operating system or environment. For example, when managing system resources in POSIX, setrlimit() can be used to set limits for certain types of resources, and getrlimit() can determine how many resources are available.
Attack patterns
HTTP DoS (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 15 Jan 2026, 12:42 UTC

WeaknessesCWE-772

Technical details

References

Community reviews

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