Windows Kernel
CVE-2020-17087 — Windows Kernel Local Elevation of Privilege Vulnerability
Important
CVSS 7.8
EPSS 0.05387
⚠️ Exploited in the wild
📢 Publicly disclosed
🔬 Patch diffed
2020-11 archive
Executive Summary
None
Overview
7.8
CVSS HIGH
Important
MS Severity
Exploited
MS Exploit Status
Exploitation Detected
MS Exploit Likelihood
CVSS Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
ATTACK VECTOR
Local
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
Low
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
High
INTEGRITY
High
AVAILABILITY
High
EXPLOIT CODE MATURITY
Functional
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 7.2
EPSS Score
0.05387
probability of exploitation in the next 30 days
0.91827 percentile - updated 2026-07-25
View on FIRST.org
Affected Products
30 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| Windows 10 for 32-bit Systems | 4586787 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 for x64-based Systems | 4586787 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1607 for 32-bit Systems | 4586830 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1607 for x64-based Systems | 4586830 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1803 for 32-bit Systems | 4586785 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1803 for ARM64-based Systems | 4586785 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1803 for x64-based Systems | 4586785 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1809 for 32-bit Systems | 4586793 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1809 for ARM64-based Systems | 4586793 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1809 for x64-based Systems | 4586793 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1903 for 32-bit Systems | 4586786 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1903 for ARM64-based Systems | 4586786 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1903 for x64-based Systems | 4586786 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1909 for 32-bit Systems | 4586786 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1909 for ARM64-based Systems | 4586786 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1909 for x64-based Systems | 4586786 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 2004 for 32-bit Systems | 4586781 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 2004 for ARM64-based Systems | 4586781 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 2004 for x64-based Systems | 4586781 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 20H2 for 32-bit Systems | 4586781 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 20H2 for ARM64-based Systems | 4586781 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 7 for 32-bit Systems Service Pack 1 4586827 (Monthly Rollup) 4586805 (Security Only) Important Elevation of Privilege 4580345 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586827 4586805 Windows 7 for x64-based Systems Service Pack 1 4586827 (Monthly Rollup) 4586805 (Security Only) Important Elevation of Privilege 4580345 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586827 4586805 Windows 8.1 for 32-bit systems 4586845 (Monthly Rollup) 4586823 (Security Only) Important Elevation of Privilege 4580347 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586845 4586823 Windows 8.1 for x64-based systems 4586845 (Monthly Rollup) 4586823 (Security Only) Important Elevation of Privilege 4580347 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586845 4586823 Windows RT 8.1 | 4586845 (Monthly Rollup) |
Important | Elevation of Privilege | Yes |
| Windows Server 2008 for 32-bit Systems Service Pack 2 4586807 (Monthly Rollup) 4586817 (Security Only) Important Elevation of Privilege 4580378 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586807 4586817 Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) 4586807 (Monthly Rollup) 4586817 (Security Only) Important Elevation of Privilege 4580378 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586807 4586817 Windows Server 2008 for x64-based Systems Service Pack 2 4586807 (Monthly Rollup) 4586817 (Security Only) Important Elevation of Privilege 4580378 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586807 4586817 Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) 4586807 (Monthly Rollup) 4586817 (Security Only) Important Elevation of Privilege 4580378 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586807 4586817 Windows Server 2008 R2 for x64-based Systems Service Pack 1 4586827 (Monthly Rollup) 4586805 (Security Only) Important Elevation of Privilege 4580345 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586827 4586805 Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) 4586827 (Monthly Rollup) 4586805 (Security Only) Important Elevation of Privilege 4580345 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586827 4586805 Windows Server 2012 4598278 (Monthly Rollup) 4598297 (Security Only) Important Elevation of Privilege 4592468 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4598278 4598297 Windows Server 2012 (Server Core installation) 4598278 (Monthly Rollup) 4598297 (Security Only) Important Elevation of Privilege 4592468 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4598278 4598297 Windows Server 2012 R2 4586845 (Monthly Rollup) 4586823 (Security Only) Important Elevation of Privilege 4580347 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586845 4586823 Windows Server 2012 R2 (Server Core installation) 4586845 (Monthly Rollup) 4586823 (Security Only) Important Elevation of Privilege 4580347 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C Yes 4586845 4586823 Windows Server 2016 | 4586830 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server 2016 (Server Core installation) | 4586830 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server 2019 | 4586793 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server 2019 (Server Core installation) | 4586793 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server, version 1903 (Server Core installation) | 4586786 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server, version 1909 (Server Core installation) | 4586786 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server, version 2004 (Server Core installation) | 4586781 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server, version 20H2 (Server Core Installation) | 4586781 (Security Update) |
Important | Elevation of Privilege | Yes |
Patches
7 patches
| Article | Type | Restart |
|---|---|---|
4586787 |
Security Update | Yes |
4586830 |
Security Update | Yes |
4586785 |
Security Update | Yes |
4586793 |
Security Update | Yes |
4586786 |
Security Update | Yes |
4586781 |
Security Update | Yes |
4586845 |
Monthly Rollup | Yes |
Patch Diff
ghidriff + headless Ghidra decompile verification · cng.sys (KB4586781)
Pool buffer overflow (CWE-190 integer truncation) in cng.sys IOCTL 0x390400 handling: cng!CfgAdtpFormatPropertyBlock computes the output allocation as SrcLen*6 in 16-bit arithmetic but writes SrcLen*6 bytes of Unicode hex dump, giving a controlled-length linear NonPagedPoolNx overflow with a XX 00 XX 00 20 00 byte pattern. Reachable by any local user via DeviceIoControl on \\.\GLOBALROOT\Device\Cng (or BCryptSetContextFunctionProperty). Exploited ITW as the sandbox-escape stage of a Chrome chain (with CVE-2020-15999); full public technique via Segment Heap BlockSize attack + named-pipe DQE abuse + quota ProcessBilled decrement -> SeDebugPrivilege (PixiePoint). Patch (KB4586781, cng.sys 10.0.19041.630) replaces the inline multiply with new helper RtlUShortMult and rejects on overflow; VERIFIED 2026-07-22 via ghidriff + headless decompile (single code-changed function).
| Function | Address | Change | Note |
|---|---|---|---|
cng!CfgAdtpFormatPropertyBlock |
0x1c006245c (both builds) |
code (verified via headless decompile 2026-07-22) | 16-bit truncation: BCryptAlloc((USHORT)(SrcLen*6)) while the hex-format loop writes SrcLen*6 bytes -> NonPagedPoolNx linear overflow ('Cngb' tag), content pattern XX 00 XX 00 20 00. SrcLen>=0x2AAB triggers ((ushort)(0x2AAB*6)=2 allocated, 0x10002 written). Length also truncated to 16-bit at the CfgAdtReportFunctionPropertyOperation call site. Fix: RtlUShortMult(len,6,&out) with error-on-overflow before allocation + BCryptFree cleanup path. |
cng!RtlUShortMult |
|
added | Safe 16-bit multiply returning error on overflow; the entire fix |
cng!BCryptFree |
|
modified (no code changes) | metadata-only churn |
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
Microsoft would like to thank Qualys for co-ordinated vulnerability disclosure on identifying a regression for the Windows Server 2012 version of this security update.
Mateusz Jurczyk and Sergei Glazunov of Google Project Zero
References
On This Page