Sources: National Vulnerability Database, CVE.org, CISA KEV, FIRST EPSS
CVE-2026-108421 Overview
Out-of-bounds read in Windows File Server Resource Management Service allows an unauthorized attacker to elevate privileges over a network.
Critical Impact
Affected Products
- Microsoft Windows File Server Resource Management Service: see the vendor advisory for the exact affected versions
Discovery Timeline
- 2026-11-10: CVE-2026-108421 published to the National Vulnerability Database by secure@microsoft.com
- 2026-11-10: last updated in the NVD database
Technical Details for CVE-2026-108421
Vulnerability Analysis
CVE-2026-108421 is a Out of Bounds Read weakness (CWE-125: Out of Bounds Read) in Microsoft Windows File Server Resource Management Service. Based on its CVSS vector, the flaw can be reached over the network, needs no login, and relies on a user taking an action. The program reads memory past the end of a buffer, leaking data or crashing.
With a CVSS base score of 7.5, apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Root Cause
The weakness is classified as CWE-125: Out of Bounds Read. The program reads memory past the end of a buffer, leaking data or crashing.
Attack Vector
Based on the CVSS vector, the flaw can be reached over the network, needs no login, and relies on a user taking an action. Attack complexity is high complexity.
No exploitation in the wild is confirmed by CISA at the time of the last update. Check the references below for any vendor or researcher proof of concept.
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Detection Methods for CVE-2026-108421
Detection Strategies
- Inventory every instance of Microsoft Windows File Server Resource Management Service and compare the running version with the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Run an authenticated vulnerability scan once your scanner ships a check for this CVE.
Monitoring Recommendations
- Forward Microsoft Windows File Server Resource Management Service application, access and audit logs to your SIEM for retrospective hunting.
- Alert on new processes, configuration changes or outbound connections from the affected service.
- Track the vendor advisory and the CISA KEV catalog for changes in exploitation status.
How to Mitigate CVE-2026-108421
Immediate Actions Required
- Apply the fixed version of Microsoft Windows File Server Resource Management Service named in the vendor advisory.
- Prioritize internet facing and business critical instances first.
- Rescan after the change to confirm the exposure is closed.
Patch Information
Use the fixed version listed in the vendor advisory for Microsoft Windows File Server Resource Management Service.
Workarounds
- If patching must wait, restrict network access to the affected service and place it behind authentication or a web application firewall rule.
CWE References
- CWE-125: Out of Bounds Read More CVEs with this weakness
Technical References
This entry is built directly from NVD, CISA KEV and EPSS data. Verify fixed versions in the vendor advisory before you deploy.
Frequently asked questions
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