CVE-2026-102598 pallets CVE debrief

Who should care

Defenders and developers using Werkzeug, especially those running on Windows and NTFS, should assess exposure and prioritize patching. This includes reviewing and updating affected versions of Werkzeug, monitoring for potential exploitation attempts, and verifying and applying patches to prevent potential denial-of-service attacks.

Why it matters

CVE-2026-102598 is a vulnerability in Werkzeug's safe_join function that allows Windows device names as filenames when they have an empty ADS marker on NTFS, potentially leading to denial-of-service attacks. Defenders and developers using Werkzeug, especially those running on Windows and NTFS, should assess exposure and prioritize patching.

• Potential denial-of-service attacks due to infinite hang when reading files with special device names
• Need to verify and apply patches to prevent exploitation
• Importance of monitoring for potential exploitation attempts

Technical summary

Werkzeug's safe_join function allows Windows device names as filenames when they have an empty ADS marker on NTFS. This can cause a denial-of-service attack when the application is running on Windows and NTFS, and the requested path ends with a special device name. The vulnerability affects Werkzeug users running on Windows and NTFS. Defenders should prioritize verifying and applying the patch to prevent potential denial-of-service attacks. Technical details indicate a high severity vulnerability due to the potential for infinite hang when reading files with special device names.

Defensive priority

Defenders should prioritize verifying and applying the patch to prevent potential denial-of-service attacks.

Recommended defensive actions

• Verify and apply the patch to prevent potential denial-of-service attacks
• Review and update affected versions of Werkzeug
• Monitor for potential exploitation attempts
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and source item provide details on the vulnerability in Werkzeug's safe_join function, which allows Windows device names as filenames when they have an empty ADS marker on NTFS. Evidence is limited to public CVE and source item information. Defenders should verify and apply patches to prevent potential exploitation. The CVE record and source item provide details on the vulnerability in Werkzeug's safe_join function, which allows Windows device names as filenames when they have an empty ADS marker on NTFS. Evidence is .

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.