How severe is CVE-2026-102598?

No CVSS score has been assigned to CVE-2026-102598 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-102598?

CVE-2026-102598 affects the following packages: werkzeug (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-102598?

Update werkzeug to 3.1.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-102598 is resolved across your whole dependency graph.

How do I detect CVE-2026-102598 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for werkzeug, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-102598 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-102598 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-102598 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-102598?

CVE-2026-102598 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 29th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-102598?

CVE-2026-102598 is classified as CWE-67 (CWE-67). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-102598 published, and has it been updated?

CVE-2026-102598 was published on September 29, 2026 and was last updated on October 15, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2026-102598: werkzeug — Fixed in 3.1.9

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-102598.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs29th percentile — riskier than 29% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍werkzeug

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`werkzeug`	all versions	3.1.9`pip install --upgrade 'werkzeug==3.1.9'`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for werkzeug, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update werkzeug to 3.1.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-102598 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Product	Fixed in	Advisory
Red Hat AI Inference Server 3.4	`rhaii/vllm-cpu-rhel9:1791857301`	RHSA-2026:83112
Red Hat AI Inference Server 3.4	`rhaii/vllm-cuda-rhel9:1791857183`	RHSA-2026:83120
Red Hat AI Inference Server 3.5	`rhaii/vllm-gaudi-rhel9:1791427182`	RHSA-2026:82061
Red Hat AI Inference Server 3.5	`rhaii/vllm-cuda-rhel9:1791473631`	RHSA-2026:82368
Red Hat AI Inference Server 3.5	`rhaii/vllm-cpu-rhel9:1791473614`	RHSA-2026:82415

Frequently Asked Questions

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 indefinit

O3 Security · Impact-Aware SCA

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CVE-2026-102598 — werkzeug