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CVE-2026-102598

Werkzeug safe_join() allows Windows special device names

6.3 MediumFix available

Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the safe_join function used by send_from_directory can allow a NUL: special-device path because safe_join checks the Windows device name without first removing an empty NTFS ADS marker. The trigger is that an application runs on Windows with NTFS and serves a user-specified path ending in a special device name such as NUL:. The attack mechanism is that a requested path ends in a Windows special device name with an empty ADS marker. The impact is that the special device opens successfully and the file read hangs indefinitely. This issue is fixed in version 3.1.9.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
Low

Exploit likelihood

0.37%Unchanged since Sep 30, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.3

Werkzeug safe_join() allows Windows special device names

Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the safe_join function used by send_from_directory can allow a NUL: special-device path because safe_join checks the Windows device name without first removing an empty NTFS ADS marker. The trigger is that an application runs on Windows with NTFS and serves a user-specified path ending in a special device name such as NUL:. The attack mechanism is that a requested path ends in a Windows special device name with an empty ADS marker. The impact is that the special device opens successfully and the file read hangs indefinitely. This issue is fixed in version 3.1.9.

Record
CVE-2026-102598
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-67
Updated
2026-11-02
EUVDEUVD-2026-88980 6.3

Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the safe_join function used by send_from_directory can allow a NUL: special-device path because safe_join checks the Windows device name without first removing an empty NTFS ADS marker. The trigger is that an application runs on Windows with NTFS and serves a user-specified path ending in a special device name such as NUL:. The attack mechanism is that a requested path ends in a Windows special device name with an empty ADS marker. The impact is that the special device opens successfully and the file read hangs indefinitely. This issue is fixed in version 3.1.9.

Record
EUVD-2026-88980
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-g6x2-hccm-hh4m 6.3

Werkzeug safe_join() allows Windows special device names

Werkzeug's safe_join function allows Windows device names as filenames when they have an empty ADS marker on NTFS.

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 Windows allows special device names with an empty ADS marker, such as 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 NTFS, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely.

Record
GHSA-g6x2-hccm-hh4m
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-67
Updated
2026-11-02
NVD 6.3

Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the safe_join function used by send_from_directory can allow a NUL: special-device path because safe_join checks the Windows device name without first removing an empty NTFS ADS marker. The trigger is that an application runs on Windows with NTFS and serves a user-specified path ending in a special device name such as NUL:. The attack mechanism is that a requested path ends in a Windows special device name with an empty ADS marker. The impact is that the special device opens successfully and the file read hangs indefinitely. This issue is fixed in version 3.1.9.

Record
CVE-2026-102598
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weakness
CWE-67
Updated
2026-11-02
OSV 6.3

Werkzeug safe_join() allows Windows special device names

Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the safe_join function used by send_from_directory can allow a NUL: special-device path because safe_join checks the Windows device name without first removing an empty NTFS ADS marker. The trigger is that an application runs on Windows with NTFS and serves a user-specified path ending in a special device name such as NUL:. The attack mechanism is that a requested path ends in a Windows special device name with an empty ADS marker. The impact is that the special device opens successfully and the file read hangs indefinitely. This issue is fixed in version 3.1.9.

Record
CVE-2026-102598
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-67
Updated
2026-11-02
OSVGHSA-g6x2-hccm-hh4m 6.3

Werkzeug safe_join() allows Windows special device names

Werkzeug's safe_join function allows Windows device names as filenames when they have an empty ADS marker on NTFS.

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 Windows allows special device names with an empty ADS marker, such as 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 NTFS, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely.

Record
GHSA-g6x2-hccm-hh4m
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-67
Updated
2026-11-02
Show 9 moreShow less
OSVPYSEC-2026-4312 6.3

Werkzeug safe_join() allows Windows special device names

Werkzeug's safe_join function allows Windows device names as filenames when they have an empty ADS marker on NTFS.

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 Windows allows special device names with an empty ADS marker, such as 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 NTFS, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely.

Record
PYSEC-2026-4312
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Updated
2026-11-02
OSVUBUNTU-CVE-2026-102598 6.3

Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the safe_join function used by send_from_directory can allow a NUL: special-device path because safe_join checks the Windows device name without first removing an empty NTFS ADS marker. The trigger is that an application runs on Windows with NTFS and serves a user-specified path ending in a special device name such as NUL:. The attack mechanism is that a requested path ends in a Windows special device name with an empty ADS marker. The impact is that the special device opens successfully and the file read hangs indefinitely. This issue is fixed in version 3.1.9.

Record
UBUNTU-CVE-2026-102598
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Updated
2026-11-02
OSVAZL-105654 No score

CVE-2026-102598 affecting package python-tensorboard 2.16.2-6

Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the safe_join function used by send_from_directory can allow a NUL: special-device path because safe_join checks the Windows device name without first removing an empty NTFS ADS marker. The trigger is that an application runs on Windows with NTFS and serves a user-specified path ending in a special device name such as NUL:. The attack mechanism is that a requested path ends in a Windows special device name with an empty ADS marker. The impact is that the special device opens successfully and the file read hangs indefinitely. This issue is fixed in version 3.1.9.

Record
AZL-105654
Updated
2026-11-02
OSVAZL-105681 No score

CVE-2026-102598 affecting package python-werkzeug 3.0.3-2

Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the safe_join function used by send_from_directory can allow a NUL: special-device path because safe_join checks the Windows device name without first removing an empty NTFS ADS marker. The trigger is that an application runs on Windows with NTFS and serves a user-specified path ending in a special device name such as NUL:. The attack mechanism is that a requested path ends in a Windows special device name with an empty ADS marker. The impact is that the special device opens successfully and the file read hangs indefinitely. This issue is fixed in version 3.1.9.

Record
AZL-105681
Updated
2026-11-02
OSVAZL-105921 No score

CVE-2026-102598 affecting package tensorflow 2.16.1-11

Werkzeug is a comprehensive WSGI web application library. Prior to 3.1.9, the safe_join function used by send_from_directory can allow a NUL: special-device path because safe_join checks the Windows device name without first removing an empty NTFS ADS marker. The trigger is that an application runs on Windows with NTFS and serves a user-specified path ending in a special device name such as NUL:. The attack mechanism is that a requested path ends in a Windows special device name with an empty ADS marker. The impact is that the special device opens successfully and the file read hangs indefinitely. This issue is fixed in version 3.1.9.

Record
AZL-105921
Updated
2026-11-02
OSVCLSA-2026-1791363861 No score

TuxCare security update for werkzeug (1 CVE)

TuxCare rebuilt werkzeug to address 1 CVE. Fixed in 2.3.8.post4+tuxcare.

Record
CLSA-2026-1791363861
Updated
2026-11-02
OSVCLSA-2026-1791365297 No score

TuxCare security update for werkzeug (2 CVEs)

TuxCare rebuilt werkzeug to address 2 CVEs. Fixed in 2.2.3.post6+tuxcare.

Record
CLSA-2026-1791365297
Updated
2026-11-02
OSVCLSA-2026-1791366853 No score

TuxCare security update for werkzeug (1 CVE)

TuxCare rebuilt werkzeug to address 1 CVE. Fixed in 1.0.1.post7+tuxcare.

Record
CLSA-2026-1791366853
Updated
2026-11-02
OSVopenSUSE-SU-2026:11943-1 No score

python313-Werkzeug-3.1.9-1.1 on GA media

These are all security issues fixed in the python313-Werkzeug-3.1.9-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:11943-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
werkzeug
PyPI
 before 3.1.9
3.1.9
python-tensorboard
Azure Linux:3
 through 2.16.2-6 None known
python-werkzeug
Azure Linux:3
 through 3.0.3-2 None known
tensorflow
Azure Linux:3
 through 2.16.1-11 None known
werkzeug
TuxCare:PyPI
 2.3.8 up to 2.3.8.post4+tuxcare, plus listed versions
2.3.8.post1+tuxcare2.3.8.post2+tuxcare2.3.8.post3+tuxcare
2.3.8.post4+tuxcare
werkzeug
TuxCare:PyPI
From an advisory covering 2 CVEs
 2.2.3 up to 2.2.3.post6+tuxcare, plus listed versions
2.2.3.post1+tuxcare2.2.3.post3+tuxcare2.2.3.post4+tuxcare2.2.3.post5+tuxcare
2.2.3.post6+tuxcare
werkzeug
TuxCare:PyPI
 1.0.1 up to 1.0.1.post7+tuxcare, plus listed versions
1.0.1.post1+tuxcare1.0.1.post2+tuxcare1.0.1.post3+tuxcare1.0.1.post4+tuxcare1.0.1.post5+tuxcare1.0.1.post6+tuxcare
1.0.1.post7+tuxcare
werkzeug
PyPI
 before 3.1.9, plus listed versions
0.10.100.10.10.10.20.10.3
Show 45 moreShow less
0.10.40.110.11.10.11.100.11.110.11.120.11.130.11.140.11.150.11.20.11.30.11.40.11.50.11.60.11.70.11.80.11.90.120.12.10.12.20.130.140.14.10.15.00.15.10.15.20.15.30.15.40.15.50.15.60.16.00.16.10.20.30.3.10.40.4.10.50.5.10.60.6.10.6.20.70.7.10.7.2
3.1.9
python-werkzeug
Ubuntu:Pro:16.04:LTS
 All versions, plus listed versions
0.10.4+dfsg1-1ubuntu10.10.4+dfsg1-1ubuntu1.10.10.4+dfsg1-1ubuntu1.20.10.4+dfsg1-1ubuntu1.2+esm10.10.4+dfsg1-1ubuntu1.2+esm2
 None known
python-werkzeug
Ubuntu:Pro:18.04:LTS
 All versions, plus listed versions
0.12.2+dfsg1-20.13+dfsg1-10.14.1+dfsg1-10.14.1+dfsg1-1ubuntu0.10.14.1+dfsg1-1ubuntu0.20.14.1+dfsg1-1ubuntu0.2+esm1
 None known
Show 6 moreShow less
Affected packages
PackageAffectedFixed
python-werkzeug
Ubuntu:20.04:LTS
 All versions, plus listed versions
0.14.1+dfsg1-40.15.6+dfsg1-10.16.0+dfsg1-10.16.1+dfsg1-1ubuntu10.16.1+dfsg1-20.16.1+dfsg1-2ubuntu0.10.16.1+dfsg1-2ubuntu0.2
 None known
python-werkzeug
Ubuntu:22.04:LTS
 All versions, plus listed versions
1.0.1+dfsg1-22.0.2+dfsg1-12.0.2+dfsg1-1ubuntu0.22.04.12.0.2+dfsg1-1ubuntu0.22.04.22.0.2+dfsg1-1ubuntu0.22.04.3
 None known
python-werkzeug
Ubuntu:24.04:LTS
 All versions, plus listed versions
2.2.2-33.0.1-13.0.1-23.0.1-33.0.1-3ubuntu0.13.0.1-3ubuntu0.2
 None known
python-werkzeug
Ubuntu:26.10
 All versions, plus listed versions
3.1.5-13.1.8-1
 None known
python-werkzeug
Ubuntu:26.04:LTS
 All versions, plus listed versions
3.1.3-23.1.4-13.1.5-1
 None known
python-Werkzeug
openSUSE:Tumbleweed
From an advisory covering 6 CVEs
 before 3.1.9-1.1
3.1.9-1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-102598 is a medium vulnerability (CVSS 6.3) in Pallets Werkzeug, published September 29, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.37%, the 31st percentile. Fixed in werkzeug 3.1.9.

References

Show 11 moreShow less
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Left out here: 56 versions. The JSON record has them.

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