SMB data disclosure via unintended guest fallback
Published May 11, 2021 · Updated Aug 3, 2024
Security-feature bypass in Microsoft Windows SMB Client allows remote attackers to read SMB data after required user interaction. The SMB2 client leaves guest fallback enabled by default instead of enforcing the operating-system edition and Group Policy settings. A user must initiate an SMB connection to a malicious or intercepted server; the resulting unsigned, unencrypted guest session exposes SMB data but provides no integrity or availability impact.
Summary
What happened
Security-feature bypass in Microsoft Windows SMB Client allows remote attackers to read SMB data after required user interaction. The SMB2 client leaves guest fallback enabled by default instead of enforcing the operating-system edition and Group Policy settings. A user must initiate an SMB connection to a malicious or intercepted server; the resulting unsigned, unencrypted guest session exposes SMB data but provides no integrity or availability impact.
The record
- CVE
- CVE-2021-31205
- Published
- May 11, 2021
- Updated
- Aug 3, 2024
- Vendor
- Microsoft
- Product
- Windows Server, version 2004
- Classifications
- T1557.001
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 11, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record 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=10.0.0 <10.0.19041.982
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
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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