CVE-2026-21860: Werkzeug safe_join() allows Windows special device names with compound extensions
CVE-2026-21860 key facts
- CISA KEV
- Not listed (catalogue checked )
- Highest advisory rating
- Critical
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N· base score 6.3, scored by GitHub_MAttack vector: network. Attack complexity: low. Attack requirements: present. Privileges required: none. User interaction: none. Confidentiality impact on the vulnerable system: none. Integrity impact on the vulnerable system: none. Availability impact on the vulnerable system: low. Confidentiality impact on subsequent systems: none. Integrity impact on subsequent systems: none. Availability impact on subsequent systems: none.- Weakness
- CWE-67: Improper Handling of Windows Device Names
- EPSS
- 0.47% chance of exploitation in the next 30 days (41st percentile). FIRST EPSS, .
- CISA SSVC
- Exploitation: none observed. Automatable: no. Technical impact: partial. CISA, .
- Vendor advisories
- 1 from Splunk
- Assigned by
- GitHub_M (CNA)
- CVE record published
- Listed by VulniPulse
Ratings, versions and fixes are quoted from the vendor advisories that cover only CVE-2026-21860; each belongs to its advisory, not to every product listed. How records are collected and checked.
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.
Text from the CVE.org record (GitHub_M).
Vendor advisories for CVE-2026-21860
Splunk
1 advisory- Advisory severityCritical
Critical [CVE-2025-13465 +86] Third-Party Package Updates in Splunk SOAR - August 2026
SVD-2026-0805Source published
This bulletin covers 87 CVEs. The products, versions, score and guidance below describe the bulletin; check its source for applicability to this specific CVE.
Splunk remedied common vulnerabilities and exposures (CVEs) in Third Party Packages in Splunk SOAR version 8.6.0, and higher. Affected product named by the advisory: Splunk SOAR 8.6.
- Affected products in this advisory
- Splunk SOAR 8.6
- Source-reported affected versions
- Splunk SOAR Below 8.6.0
- Source-reported fixed versions
- Splunk SOAR 8.6.0
- Mitigation guidance
- Upgrade Splunk SOAR to version 8.6.0, or higher.
References
Timeline
- CVE record published
- CVE record last updated
- First vendor advisory listed by VulniPulse
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