Common Log File System Driver
CVE-2020-0639 — Windows Common Log File System Driver Information Disclosure Vulnerability
Executive Summary
An information disclosure vulnerability exists in the Windows Common Log File System (CLFS) driver when it fails to properly handle objects in memory. An attacker who successfully exploited this vulnerability could potentially read data that was not intended to be disclosed. Note that this vulnerability would not allow an attacker to execute code or to elevate their user rights directly, but it could be used to obtain information that could be used to try to further compromise the affected system. To exploit the vulnerability, an attacker would first have to log on to the system, and then run a specially crafted application to take control over the affected system. The security update addresses the vulnerability by correcting how CLFS handles objects in memory.
Overview
5.5
CVSS MEDIUM
Important
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
CVSS Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C
ATTACK VECTOR
Local
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
Low
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
High
INTEGRITY
None
AVAILABILITY
None
EXPLOIT CODE MATURITY
Proof-of-Concept
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 5.0
EPSS Score
0.01307
probability of exploitation in the next 30 days
0.67606 percentile - updated 2026-07-25
View on FIRST.org
Affected Products
27 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| Windows 10 for 32-bit Systems | 4534306 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 for x64-based Systems | 4534306 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1607 for 32-bit Systems | 4534271 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1607 for x64-based Systems | 4534271 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1709 for 32-bit Systems | 4534276 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1709 for ARM64-based Systems | 4534276 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1709 for x64-based Systems | 4534276 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1803 for 32-bit Systems | 4534293 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1803 for ARM64-based Systems | 4534293 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1803 for x64-based Systems | 4534293 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1809 for 32-bit Systems | 4534273 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1809 for ARM64-based Systems | 4534273 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1809 for x64-based Systems | 4534273 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1903 for 32-bit Systems | 4528760 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1903 for ARM64-based Systems | 4528760 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1903 for x64-based Systems | 4528760 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1909 for 32-bit Systems | 4528760 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1909 for ARM64-based Systems | 4528760 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 10 Version 1909 for x64-based Systems | 4528760 (Security Update) |
Important | Information Disclosure | Yes |
| Windows 7 for 32-bit Systems Service Pack 1 4534310 (Monthly Rollup) 4534314 (Security Only) Important Information Disclosure 4530734 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes 4534310 Windows 7 for x64-based Systems Service Pack 1 4534310 (Monthly Rollup) 4534314 (Security Only) Important Information Disclosure 4530734 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes 4534310 Windows 8.1 for 32-bit systems 4534297 (Monthly Rollup) 4534309 (Security Only) Important Information Disclosure 4530702 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes 4534297 4534309 Windows 8.1 for x64-based systems 4534297 (Monthly Rollup) 4534309 (Security Only) Important Information Disclosure 4530702 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes 4534297 4534309 Windows RT 8.1 | 4534297 (Monthly Rollup) |
Important | Information Disclosure | Yes |
| Windows Server 2008 for 32-bit Systems Service Pack 2 4534303 (Monthly Rollup) 4534312 (Security Only) Important Information Disclosure 4530695 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes None Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) 4534303 (Monthly Rollup) 4534312 (Security Only) Important Information Disclosure 4530695 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes None Windows Server 2008 for Itanium-Based Systems Service Pack 2 4534303 (Monthly Rollup) 4534312 (Security Only) Important Information Disclosure 4530695 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes None Windows Server 2008 for x64-based Systems Service Pack 2 4534303 (Monthly Rollup) 4534312 (Security Only) Important Information Disclosure 4530695 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes None Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) 4534303 (Monthly Rollup) 4534312 (Security Only) Important Information Disclosure 4530695 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes None Windows Server 2008 R2 for Itanium-Based Systems Service Pack 1 4534310 (Monthly Rollup) 4534314 (Security Only) Important Information Disclosure 4530734 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes 4534310 Windows Server 2008 R2 for x64-based Systems Service Pack 1 4534310 (Monthly Rollup) 4534314 (Security Only) Important Information Disclosure 4530734 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes 4534310 Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) 4534310 (Monthly Rollup) 4534314 (Security Only) Important Information Disclosure 4530734 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes 4534310 Windows Server 2012 4534283 (Monthly Rollup) 4534288 (Security Only) Important Information Disclosure 4530691 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes 4534283 4534288 Windows Server 2012 (Server Core installation) 4534283 (Monthly Rollup) 4534288 (Security Only) Important Information Disclosure 4530691 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes 4534283 4534288 Windows Server 2012 R2 4534297 (Monthly Rollup) 4534309 (Security Only) Important Information Disclosure 4530702 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes 4534297 4534309 Windows Server 2012 R2 (Server Core installation) 4534297 (Monthly Rollup) 4534309 (Security Only) Important Information Disclosure 4530702 Base: 5.5 Temporal: 5.0 Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C Yes 4534297 4534309 Windows Server 2016 | 4534271 (Security Update) |
Important | Information Disclosure | Yes |
| Windows Server 2016 (Server Core installation) | 4534271 (Security Update) |
Important | Information Disclosure | Yes |
| Windows Server 2019 | 4534273 (Security Update) |
Important | Information Disclosure | Yes |
| Windows Server 2019 (Server Core installation) | 4534273 (Security Update) |
Important | Information Disclosure | Yes |
| Windows Server, version 1803 (Server Core Installation) | 4534293 (Security Update) |
Important | Information Disclosure | Yes |
| Windows Server, version 1903 (Server Core installation) | 4528760 (Security Update) |
Important | Information Disclosure | Yes |
| Windows Server, version 1909 (Server Core installation) | 4528760 (Security Update) |
Important | Information Disclosure | Yes |
Patches
7 patches
| Article | Type | Restart |
|---|---|---|
4534306 |
Security Update | Yes |
4534271 |
Security Update | Yes |
4534276 |
Security Update | Yes |
4534293 |
Security Update | Yes |
4534273 |
Security Update | Yes |
4528760 |
Security Update | Yes |
4534297 |
Monthly Rollup | Yes |
Known Exploits
No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.
Acknowledgments
Anonymous working with Trend Micro's Zero Day Initiative
References
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