How severe is CVE-2026-27199?

CVE-2026-27199 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-2026-27199 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-27199?

CVE-2026-27199 affects Palletsprojects Werkzeug. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-27199?

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

Does CVE-2026-27199 have an EU (EUVD) identifier?

Yes. CVE-2026-27199 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-7732.

When was CVE-2026-27199 published?

CVE-2026-27199 was published on 2026-02-21 and last updated on 2026-06-17.

CVE-2026-27199

CVE-2026-27199 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: 1% (42nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-7732
Weakness: CWE-67
Affected product: Palletsprojects Werkzeug
Published: 2026-02-21
Last modified: 2026-06-17

Description

Werkzeug is a comprehensive WSGI web application library. Versions 3.1.5 and below, the safe_join function allows Windows device names as filenames if preceded by other path segments. This was previously reported as GHSA-hgf8-39gv-g3f2, but the added filtering failed to account for the fact that safe_join accepts paths with multiple segments, such as example/NUL. The function send_from_directory uses safe_join to safely serve files at user-specified paths under a directory. If the application is running on Windows, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely. This issue has been fixed in version 3.1.6.

Frequently asked questions

What is CVE-2026-27199?: Werkzeug is a comprehensive WSGI web application library. Versions 3.1.5 and below, the safe_join function allows Windows device names as filenames if preceded by other path segments. This was previously reported as GHSA-hgf8-39gv-g3f2, but the added filtering failed to account for the fact that safe_join accepts paths with multiple segments, such as example/NUL. The function send_from_directory uses safe_join to safely serve files at user-specified paths under a directory. If the application is running on Windows, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely. This issue has been fixed in version 3.1.6.
How severe is CVE-2026-27199?: CVE-2026-27199 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-2026-27199 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-27199?: CVE-2026-27199 affects Palletsprojects Werkzeug. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-27199?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-27199 have an EU (EUVD) identifier?: Yes. CVE-2026-27199 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-7732.
When was CVE-2026-27199 published?: CVE-2026-27199 was published on 2026-02-21 and last updated on 2026-06-17.

References

Affected products (1)

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

More vulnerabilities in Palletsprojects Werkzeug

CVE-2022-29361 — Critical (CVSS 9.8): Improper parsing of HTTP requests in Pallets Werkzeug v2.1.0 and below allows attackers to perform HTTP Request…
CVE-2023-46136 — High (CVSS 8.0): Werkzeug is a comprehensive WSGI web application library. In versions on the 3.x branch prior to 3.0.1 and on the 2.x…
CVE-2024-49767 — High (CVSS 7.5): Werkzeug is a Web Server Gateway Interface web application library. Applications using…
CVE-2024-34069 — High (CVSS 7.5): Werkzeug is a comprehensive WSGI web application library. The debugger in affected versions of Werkzeug can allow an…
CVE-2023-25577 — High (CVSS 7.5): Werkzeug is a comprehensive WSGI web application library. Prior to version 2.2.3, Werkzeug's multipart form data parser…
CVE-2019-14806 — High (CVSS 7.5): Pallets Werkzeug before 0.15.3, when used with Docker, has insufficient debugger PIN randomness because Docker…

All CVEs affecting Palletsprojects Werkzeug →

Other CWE-67 vulnerabilities

CVE-2024-51745 — Critical (CVSS 10.0): Wasmtime is a fast and secure runtime for WebAssembly. Wasmtime's filesystem sandbox implementation on Windows blocks…
CVE-2024-35197 — Medium (CVSS 5.4): gitoxide is a pure Rust implementation of Git. On Windows, fetching refs that clash with legacy device names reads from…
CVE-2026-21860 — Medium (CVSS 5.3): Werkzeug is a comprehensive WSGI web application library. Prior to version 3.1.5, Werkzeug's safe_join function allows…
CVE-2025-66221 — Medium (CVSS 5.3): Werkzeug is a comprehensive WSGI web application library. Prior to version 3.1.4, Werkzeug's safe_join function allows…

Browse all CWE-67 vulnerabilities →