CVE-2021-1731

Private-key disclosure via weak SID-protected PFX encryption

Published Feb 25, 2021 · Updated Aug 3, 2024

PFX encryption bypass in affected Windows 10 and Windows Server releases allows attackers to read private keys from protected PFX files. SID-protected PFX export improperly protects AES-encrypted keys, leaving the exported private-key material recoverable despite SID protection. Exploitation requires user interaction to export such a file and attacker access to it; the documented consequence is confidentiality loss only.

CVSS severity5.5
Medium
EPSS probability0.88%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

PFX encryption bypass in affected Windows 10 and Windows Server releases allows attackers to read private keys from protected PFX files. SID-protected PFX export improperly protects AES-encrypted keys, leaving the exported private-key material recoverable despite SID protection. Exploitation requires user interaction to export such a file and attacker access to it; the documented consequence is confidentiality loss only.

The record

CVE
CVE-2021-1731
Published
Feb 25, 2021
Updated
Aug 3, 2024
Vendor
Microsoft
Product
Windows Server 2019
Classifications
CWE-522, T1552.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 25, 2021CVE publishedPublication date reported by the CVE source.
  2. 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.

  1. Affected versionversion=10.0.0 <publication

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Microsoft · Windows Server 2019version=10.0.0 <publication
Microsoft · Windows 10 Version 1909version=10.0.0 <publication
Microsoft · Windows 10 Version 1803version=10.0.0 <publication
Microsoft · Windows Server, version 2004version=10.0.0 <publication
Microsoft · Windows 10 Version 20H2version=10.0.0 <publication
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.0 <publication
Microsoft · Windows Server version 20H2version=10.0.0 <publication
Microsoft · Windows 10 Version 2004version=10.0.0 <publication
Microsoft · Windows 10 Version 1809version=10.0.0 <publication
Microsoft · Windows Server, version 1909 (Server Core installation)version=10.0.0 <publication

Published CVSS scores

5.5Microsoft CorporationCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
2.1NIST NVDAV:L/AC:L/Au:N/C:P/I:N/A:N
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-522Insufficiently Protected Credentials
T1552.004Unsecured Credentials: Private Keys

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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