SYSTEM privilege escalation via UDFS heap overflow
Published Jun 9, 2026 · Updated Jun 9, 2026
Heap-based buffer overflow in Microsoft Windows UDFS allows local users with low privileges to execute code as SYSTEM. Microsoft maps the flaw to numeric truncation and a heap-based overflow but has not disclosed the affected routine or malformed input field. Exploitation requires local low-privileged access and no user interaction, granting complete control of the affected installation.
Summary
What happened
Heap-based buffer overflow in Microsoft Windows UDFS allows local users with low privileges to execute code as SYSTEM. Microsoft maps the flaw to numeric truncation and a heap-based overflow but has not disclosed the affected routine or malformed input field. Exploitation requires local low-privileged access and no user interaction, granting complete control of the affected installation.
The record
- CVE
- CVE-2026-40404
- Published
- Jun 9, 2026
- Updated
- Jun 9, 2026
- Vendor
- Microsoft
- Product
- Windows Server 2019
- Classifications
- CWE-122, CWE-197, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jun 9, 2026CVE publishedPublication date reported by the CVE source.
- Jun 9, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=10.0.17763.0 <10.0.17763.8880
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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