Windows IIS
CVE-2020-0645 — Microsoft IIS Server Tampering Vulnerability
Executive Summary
A tampering vulnerability exists when Microsoft IIS Server improperly handles malformed request headers. An attacker who successfully exploited the vulnerability could cause a vulnerable server to improperly process HTTP headers and tamper with the responses returned to clients. To exploit the vulnerability, an attacker would need to send a malformed HTTP request to an affected server. The update addresses the vulnerability by modifying how IIS Server handles malformed request headers.
Overview
7.5
CVSS HIGH
Important
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C
ATTACK VECTOR
Network
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
None
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
None
INTEGRITY
High
AVAILABILITY
None
EXPLOIT CODE MATURITY
Proof-of-Concept
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 6.7
EPSS Score
0.03809
probability of exploitation in the next 30 days
0.8865 percentile - updated 2026-06-21
View on FIRST.org
Affected Products
27 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| Windows 10 for 32-bit Systems | 4540693 (Security Update) |
Important | Tampering | Yes |
| Windows 10 for x64-based Systems | 4540693 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1607 for 32-bit Systems | 4540670 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1607 for x64-based Systems | 4540670 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1709 for 32-bit Systems | 4540681 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1709 for ARM64-based Systems | 4540681 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1709 for x64-based Systems | 4540681 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1803 for 32-bit Systems | 4540689 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1803 for ARM64-based Systems | 4540689 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1803 for x64-based Systems | 4540689 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1809 for 32-bit Systems | 4538461 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1809 for ARM64-based Systems | 4538461 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1809 for x64-based Systems | 4538461 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1903 for 32-bit Systems | 4540673 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1903 for ARM64-based Systems | 4540673 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1903 for x64-based Systems | 4540673 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1909 for 32-bit Systems | 4540673 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1909 for ARM64-based Systems | 4540673 (Security Update) |
Important | Tampering | Yes |
| Windows 10 Version 1909 for x64-based Systems | 4540673 (Security Update) |
Important | Tampering | Yes |
| Windows 7 for 32-bit Systems Service Pack 1 4540688 (Monthly Rollup) 4541500 (Security Only) Important Tampering 4537820 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4540688 4541500 Windows 7 for x64-based Systems Service Pack 1 4540688 (Monthly Rollup) 4541500 (Security Only) Important Tampering 4537820 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4540688 4541500 Windows 8.1 for 32-bit systems 4541509 (Monthly Rollup) 4541505 (Security Only) Important Tampering 4537821 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4541509 4541505 Windows 8.1 for x64-based systems 4541509 (Monthly Rollup) 4541505 (Security Only) Important Tampering 4537821 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4541509 4541505 Windows RT 8.1 | 4541509 (Monthly Rollup) |
Important | Tampering | Yes |
| Windows Server 2008 for 32-bit Systems Service Pack 2 4541506 (Monthly Rollup) 4541504 (Security Only) Important Tampering 4537810 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4541506 4541504 Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) 4541506 (Monthly Rollup) 4541504 (Security Only) Important Tampering 4537810 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4541506 4541504 Windows Server 2008 for x64-based Systems Service Pack 2 4541506 (Monthly Rollup) 4541504 (Security Only) Important Tampering 4537810 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4541506 4541504 Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) 4541506 (Monthly Rollup) 4541504 (Security Only) Important Tampering 4537810 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4541506 4541504 Windows Server 2008 R2 for x64-based Systems Service Pack 1 4540688 (Monthly Rollup) 4541500 (Security Only) Important Tampering 4537820 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4540688 4541500 Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) 4540688 (Monthly Rollup) 4541500 (Security Only) Important Tampering 4537820 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4540688 4541500 Windows Server 2012 4541510 (Monthly Rollup) 4540694 (Security Only) Important Tampering 4537814 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4541510 4540694 Windows Server 2012 (Server Core installation) 4541510 (Monthly Rollup) 4540694 (Security Only) Important Tampering 4537814 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4541510 4540694 Windows Server 2012 R2 4541509 (Monthly Rollup) 4541505 (Security Only) Important Tampering 4537821 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4541509 4541505 Windows Server 2012 R2 (Server Core installation) 4541509 (Monthly Rollup) 4541505 (Security Only) Important Tampering 4537821 Base: 7.5 Temporal: 6.7 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/RL:O/RC:C Yes 4541509 4541505 Windows Server 2016 | 4540670 (Security Update) |
Important | Tampering | Yes |
| Windows Server 2016 (Server Core installation) | 4540670 (Security Update) |
Important | Tampering | Yes |
| Windows Server 2019 | 4538461 (Security Update) |
Important | Tampering | Yes |
| Windows Server 2019 (Server Core installation) | 4538461 (Security Update) |
Important | Tampering | Yes |
| Windows Server, version 1803 (Server Core Installation) | 4540689 (Security Update) |
Important | Tampering | Yes |
| Windows Server, version 1903 (Server Core installation) | 4540673 (Security Update) |
Important | Tampering | Yes |
| Windows Server, version 1909 (Server Core installation) | 4540673 (Security Update) |
Important | Tampering | Yes |
Patches
7 patches
| Article | Type | Restart |
|---|---|---|
4540693 |
Security Update | Yes |
4540670 |
Security Update | Yes |
4540681 |
Security Update | Yes |
4540689 |
Security Update | Yes |
4538461 |
Security Update | Yes |
4540673 |
Security Update | Yes |
4541509 |
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
Andrew Dixie, Andrew Stucki, @ZeddYu_Lu
References
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