SYSTEM code execution via decompression integer underflow
Published Jun 8, 2021 · Updated Aug 3, 2024
Integer underflow in Microsoft's Windows Cloud Files Mini Filter Driver allows local users to execute arbitrary code as SYSTEM. In cldflt.sys, HsmpRpiDecompressBuffer advances a destination pointer by 12 bytes but subtracts 12 from an attacker-controlled short length, passing a huge unsigned size to RtlDecompressBuffer and overflowing a kernel buffer. Exploitation requires prior low-privileged code execution and crafted cloud-placeholder reparse data, after which code runs with SYSTEM privileges.
Summary
What happened
Integer underflow in Microsoft's Windows Cloud Files Mini Filter Driver allows local users to execute arbitrary code as SYSTEM. In cldflt.sys, HsmpRpiDecompressBuffer advances a destination pointer by 12 bytes but subtracts 12 from an attacker-controlled short length, passing a huge unsigned size to RtlDecompressBuffer and overflowing a kernel buffer. Exploitation requires prior low-privileged code execution and crafted cloud-placeholder reparse data, after which code runs with SYSTEM privileges.
The record
- CVE
- CVE-2021-31969
- Published
- Jun 8, 2021
- Updated
- Aug 3, 2024
- Vendor
- Microsoft
- Product
- Windows Server 2019
- Classifications
- CWE-269, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jun 8, 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 <10.0.17763.1999
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
- CVE-2021-31969 Underflowing in the Clouds proof of conceptproof of concept · demonstrated
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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