Restricted file upload via filename validation bypass
Published May 21, 2020 · Updated Aug 19, 2026
Improper file validation in the BITS IIS module in Microsoft Windows allows remote authenticated users to upload restricted file types. The module accepts a crafted remote filename for an upload job without correctly enforcing filename restrictions before writing content into an IIS-hosted folder. Exploitation requires BITS upload permission and an IIS virtual directory with the BITS server extension enabled; the direct result is placement of a normally blocked file type in the hosted folder.
Summary
What happened
Improper file validation in the BITS IIS module in Microsoft Windows allows remote authenticated users to upload restricted file types. The module accepts a crafted remote filename for an upload job without correctly enforcing filename restrictions before writing content into an IIS-hosted folder. Exploitation requires BITS upload permission and an IIS virtual directory with the BITS server extension enabled; the direct result is placement of a normally blocked file type in the hosted folder.
The record
- CVE
- CVE-2020-1112
- Published
- May 21, 2020
- Updated
- Aug 19, 2026
- Vendor
- Microsoft
- Product
- Windows 10 Version 1507
- Classifications
- CWE-434, CAPEC-1, T1190
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- May 21, 2020CVE publishedPublication date reported by the CVE source.
- Aug 19, 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?
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- Affected versionversion=10.0.10240.0 <publication
What conditions does exploitation require?
What is affected?
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
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Technologies
Your stack
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Your stack
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