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Vulnerability details: VCID-jxz2-8tqb-mbeg
Vulnerability ID VCID-jxz2-8tqb-mbeg
Aliases CVE-2026-27199
GHSA-29vq-49wr-vm6x
Summary Werkzeug safe_join() allows Windows special device names Werkzeug's `safe_join` function allows Windows device names as filenames if when preceded by other path segments. This was previously reported as https://github.com/pallets/werkzeug/security/advisories/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`. `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.
Status Published
Exploitability 0.5
Weighted Severity 6.2
Risk 3.1
Affected and Fixed Packages Package Details
Weaknesses (3)
CWE-67 Improper Handling of Windows Device Names
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.0002 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.00021 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
epss 0.00021 https://api.first.org/data/v1/epss?cve=CVE-2026-27199
cvssv3.1 5.3 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv3.1_qr MODERATE https://github.com/advisories/GHSA-29vq-49wr-vm6x
cvssv4 6.3 https://github.com/pallets/werkzeug
generic_textual MODERATE https://github.com/pallets/werkzeug
cvssv4 6.3 https://github.com/pallets/werkzeug/commit/f407712fdc60a09c2b3f4fe7db557703e5d9338d
generic_textual MODERATE https://github.com/pallets/werkzeug/commit/f407712fdc60a09c2b3f4fe7db557703e5d9338d
ssvc Track https://github.com/pallets/werkzeug/commit/f407712fdc60a09c2b3f4fe7db557703e5d9338d
cvssv4 6.3 https://github.com/pallets/werkzeug/releases/tag/3.1.6
generic_textual MODERATE https://github.com/pallets/werkzeug/releases/tag/3.1.6
ssvc Track https://github.com/pallets/werkzeug/releases/tag/3.1.6
cvssv3.1_qr MODERATE https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x
cvssv4 6.3 https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x
generic_textual MODERATE https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x
ssvc Track https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x
cvssv4 6.3 https://nvd.nist.gov/vuln/detail/CVE-2026-27199
generic_textual MODERATE https://nvd.nist.gov/vuln/detail/CVE-2026-27199
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2026-27199
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://github.com/pallets/werkzeug
https://github.com/pallets/werkzeug/commit/f407712fdc60a09c2b3f4fe7db557703e5d9338d
https://github.com/pallets/werkzeug/releases/tag/3.1.6
https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x
https://nvd.nist.gov/vuln/detail/CVE-2026-27199
GHSA-29vq-49wr-vm6x https://github.com/advisories/GHSA-29vq-49wr-vm6x
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Found at https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
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 Found at https://github.com/pallets/werkzeug
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none
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 Found at https://github.com/pallets/werkzeug/commit/f407712fdc60a09c2b3f4fe7db557703e5d9338d
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:N/A:N/T:P/P:M/B:A/M:M/D:T/2026-02-24T19:02:05Z/ Found at https://github.com/pallets/werkzeug/commit/f407712fdc60a09c2b3f4fe7db557703e5d9338d
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 Found at https://github.com/pallets/werkzeug/releases/tag/3.1.6
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:N/A:N/T:P/P:M/B:A/M:M/D:T/2026-02-24T19:02:05Z/ Found at https://github.com/pallets/werkzeug/releases/tag/3.1.6
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 Found at https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:N/A:N/T:P/P:M/B:A/M:M/D:T/2026-02-24T19:02:05Z/ Found at https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x
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 Found at https://nvd.nist.gov/vuln/detail/CVE-2026-27199
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.05298
EPSS Score 0.0002
Published At April 2, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-04-01T12:52:41.200400+00:00 GithubOSV Importer Import https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-29vq-49wr-vm6x/GHSA-29vq-49wr-vm6x.json 38.0.0