How severe is CVE-2026-39844?

CVE-2026-39844 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2026-39844 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (29th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-39844?

CVE-2026-39844 affects Zauberzeug Nicegui. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-39844?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-39844 have an EU (EUVD) identifier?

Yes. CVE-2026-39844 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-20610.

When was CVE-2026-39844 published?

CVE-2026-39844 was published on 2026-04-08 and last updated on 2026-06-17.

CVE-2026-39844

CVE-2026-39844 is a medium-severity vulnerability in Zauberzeug Nicegui with a CVSS 3.x base score of 5.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-22.

Key facts

Severity: Medium (CVSS 3.x base score 5.9)
EPSS exploit prediction: 0% (29th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-20610
Weakness: CWE-22
Affected product: Zauberzeug Nicegui
Published: 2026-04-08
Last modified: 2026-06-17

Description

NiceGUI is a Python-based UI framework. Prior to 3.10.0, Since PurePosixPath only recognizes forward slashes (/) as path separators, an attacker can bypass this sanitization on Windows by using backslashes (\) in the upload filename. Applications that construct file paths using file.name (a pattern demonstrated in NiceGUI's bundled examples) are vulnerable to arbitrary file write on Windows. This vulnerability is fixed in 3.10.0.

Frequently asked questions

What is CVE-2026-39844?: NiceGUI is a Python-based UI framework. Prior to 3.10.0, Since PurePosixPath only recognizes forward slashes (/) as path separators, an attacker can bypass this sanitization on Windows by using backslashes (\) in the upload filename. Applications that construct file paths using file.name (a pattern demonstrated in NiceGUI's bundled examples) are vulnerable to arbitrary file write on Windows. This vulnerability is fixed in 3.10.0.
How severe is CVE-2026-39844?: CVE-2026-39844 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2026-39844 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (29th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-39844?: CVE-2026-39844 affects Zauberzeug Nicegui. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-39844?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-39844 have an EU (EUVD) identifier?: Yes. CVE-2026-39844 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-20610.
When was CVE-2026-39844 published?: CVE-2026-39844 was published on 2026-04-08 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:zauberzeug:nicegui:*:*:*:*:*:*:*:*

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