How severe is CVE-2026-21860?

CVE-2026-21860 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-21860 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-21860?

CVE-2026-21860 affects Palletsprojects Werkzeug. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-21860?

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

Does CVE-2026-21860 have an EU (EUVD) identifier?

Yes. CVE-2026-21860 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-1425.

When was CVE-2026-21860 published?

CVE-2026-21860 was published on 2026-01-08 and last updated on 2026-06-17.

CVE-2026-21860

CVE-2026-21860 is a medium-severity vulnerability in Palletsprojects Werkzeug with a CVSS 3.x base score of 5.3. 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-67.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v4: 6.3
EPSS exploit prediction: 0% (34th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-1425
Weakness: CWE-67
Affected product: Palletsprojects Werkzeug
Published: 2026-01-08
Last modified: 2026-06-17

Description

Werkzeug is a comprehensive WSGI web application library. Prior to version 3.1.5, Werkzeug's safe_join function allows path segments with Windows device names that have file extensions or trailing spaces. On Windows, there are special device names such as CON, AUX, etc that are implicitly present and readable in every directory. Windows still accepts them with any file extension, such as CON.txt, or trailing spaces such as CON. This issue has been patched in version 3.1.5.

Frequently asked questions

What is CVE-2026-21860?: Werkzeug is a comprehensive WSGI web application library. Prior to version 3.1.5, Werkzeug's safe_join function allows path segments with Windows device names that have file extensions or trailing spaces. On Windows, there are special device names such as CON, AUX, etc that are implicitly present and readable in every directory. Windows still accepts them with any file extension, such as CON.txt, or trailing spaces such as CON. This issue has been patched in version 3.1.5.
How severe is CVE-2026-21860?: CVE-2026-21860 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-21860 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-21860?: CVE-2026-21860 affects Palletsprojects Werkzeug. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-21860?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-21860 have an EU (EUVD) identifier?: Yes. CVE-2026-21860 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-1425.
When was CVE-2026-21860 published?: CVE-2026-21860 was published on 2026-01-08 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:palletsprojects:werkzeug:*:*:*:*:*:*:*:*

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