CVE-2024-21320Public exploitNetwork attack vector

NTLM credential disclosure via UNC theme paths

Published Jan 9, 2024 · Updated Sep 15, 2025

Information disclosure in Microsoft Windows Themes allows remote attackers to capture NTLM credentials through a crafted theme file. Explorer automatically builds a thumbnail and follows attacker-controlled UNC paths in the BrandImage or Wallpaper fields, initiating SMB authentication. A victim only needs to download or browse to the file; the resulting NTLM material supports offline password cracking or relay, but no integrity or availability impact is reported.

CVSS severity6.5
Medium
EPSS probability22.77%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in Microsoft Windows Themes allows remote attackers to capture NTLM credentials through a crafted theme file. Explorer automatically builds a thumbnail and follows attacker-controlled UNC paths in the BrandImage or Wallpaper fields, initiating SMB authentication. A victim only needs to download or browse to the file; the resulting NTLM material supports offline password cracking or relay, but no integrity or availability impact is reported.

The record

CVE
CVE-2024-21320
Published
Jan 9, 2024
Updated
Sep 15, 2025
Vendor
Microsoft
Product
Windows 10 Version 1507
Classifications
CWE-200, T1187
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 9, 2024CVE publishedPublication date reported by the CVE source.
  2. Sep 15, 2025Record 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=10.0.10240.0 <10.0.10240.20402

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Windows 10 Version 1507version=10.0.10240.0 <10.0.10240.20402
Microsoft · Windows Server 2019version=10.0.17763.0 <10.0.17763.5329
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.6614
Microsoft · Windows 11 version 21H2version=10.0.0 <10.0.22000.2713
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.9200.0 <6.2.9200.24664
Microsoft · Windows Server 2012version=6.2.9200.0 <6.2.9200.24664
Microsoft · Windows 10 Version 21H2version=10.0.19043.0 <10.0.19044.3930
Microsoft · Windows Server 2016version=10.0.14393.0 <10.0.14393.6614
Microsoft · Windows 11 Version 22H3version=10.0.22631.0 <10.0.22631.3007
Microsoft · Windows 10 Version 22H2version=10.0.19045.0 <10.0.19045.3930
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.9600.0 <6.3.9600.21765
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <10.0.17763.5329
Microsoft · Windows 11 Version 23H2version=10.0.22631.0 <10.0.22631.3007
Microsoft · Windows 11, version 22H2version=10.0.22621.0 <10.0.22621.3007
Microsoft · Windows 10 Version 1607version=10.0.14393.0 <10.0.14393.6614
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.2227
Microsoft · Windows 10 Version 1809version=10.0.0 <10.0.17763.5329; version=10.0.17763.0 <10.0.17763.5329
Microsoft · Windows Server 2012 R2version=6.3.9600.0 <6.3.9600.21765

Published CVSS scores

6.5Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
T1187Forced Authentication

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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