CVE-2020-1284 — Windows SMBv3 Client/Server Denial of Service Vulnerability

Executive Summary

A denial of service vulnerability exists in the way that the Microsoft Server Message Block 3.1.1 (SMBv3) protocol handles certain requests. An authenticated attacker who successfully exploited this vulnerability against an SMB Server could cause the affected system to crash. An unauthenticated attacker could also exploit this this vulnerability against an SMB client and cause the affected system to crash. To exploit the vulnerability against a server, an authenticated attacker could send a specially crafted packet to a targeted SMBv3 server. To exploit the vulnerability against a client, an unauthenticated attacker would need to configure a malicious SMBv3 server and convince a user to connect to it. The security update addresses the vulnerability by correcting how the SMBv3 protocol handles these specially crafted requests.

Overview

6.5

CVSS MEDIUM

Important

MS Severity

Not Exploited

MS Exploit Status

More Likely

MS Exploit Likelihood

Category Denial of Service

Released Jun 9 2020

Last Updated Jun 9 2020

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.06909 — 0.93261 percentile

NVD CVSS 6.5 MEDIUM — differs from MSRC

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C

ATTACK VECTOR

Network

ATTACK COMPLEXITY

Low

PRIVILEGES REQUIRED

None

USER INTERACTION

Required

SCOPE

Unchanged

CONFIDENTIALITY

None

INTEGRITY

None

AVAILABILITY

High

EXPLOIT CODE MATURITY

Proof-of-Concept

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 6.7

EPSS Score

0.06909

probability of exploitation in the next 30 days

0.93261 percentile - updated 2026-06-21

View on FIRST.org

Affected Products

4 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 Version 2004 for 32-bit Systems	`4557957 (Security Update)`	Important	Denial of Service	Yes
Windows 10 Version 2004 for ARM64-based Systems	`4557957 (Security Update)`	Important	Denial of Service	Yes
Windows 10 Version 2004 for x64-based Systems	`4557957 (Security Update)`	Important	Denial of Service	Yes
Windows Server, version 2004 (Server Core installation)	`4557957 (Security Update)`	Important	Denial of Service	Yes

Patches

1 patch

Article	Type	Restart
`4557957`	Security Update	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

Microsoft Platform Security Assurance & Vulnerability Research

References

MSRC Advisory MITRE NVD