CVE-2025-21308Network attack vector

NTLM hash disclosure via remote theme resources

Published Jan 14, 2025 · Updated Jun 9, 2026

Information disclosure in Windows Themes in affected Microsoft Windows builds allows remote attackers to obtain NTLM hashes via a crafted theme file. Theme-file handling follows an attacker-controlled remote resource path and automatically authenticates to that host while rendering or applying the theme. A user must load and manipulate the file; workstation folder viewing can suffice, while server exploitation requires Desktop Experience and theme application.

CVSS severity6.5
Medium
EPSS probability2.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Information disclosure in Windows Themes in affected Microsoft Windows builds allows remote attackers to obtain NTLM hashes via a crafted theme file. Theme-file handling follows an attacker-controlled remote resource path and automatically authenticates to that host while rendering or applying the theme. A user must load and manipulate the file; workstation folder viewing can suffice, while server exploitation requires Desktop Experience and theme application.

The record

CVE
CVE-2025-21308
Published
Jan 14, 2025
Updated
Jun 9, 2026
Vendor
Microsoft
Product
Windows 10 Version 1507
Classifications
CWE-200, T1187
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 14, 2025CVE publishedPublication date reported by the CVE source.
  2. Jun 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

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 <10.0.10240.20890

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Windows 10 Version 1507version=10.0.10240.0 <10.0.10240.20890
Microsoft · Windows Server 2019version=10.0.17763.0 <10.0.17763.6775
Microsoft · Windows Server 2025 (Server Core installation)version=10.0.26100.0 <10.0.26100.2894
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.7699
Microsoft · Windows 11, version 24H2version=10.0.26100.0 <10.0.26100.2894
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.9200.0 <6.2.9200.25273
Microsoft · Windows Server 2012version=6.2.9200.0 <6.2.9200.25273
Microsoft · Windows 10 Version 21H2version=10.0.19044.0 <10.0.19044.5371
Microsoft · Windows Server 2016version=10.0.14393.0 <10.0.14393.7699
Microsoft · Windows 11 Version 22H3version=10.0.22631.0 <10.0.22631.4751
Microsoft · Windows 10 Version 22H2version=10.0.19045.0 <10.0.19045.5371
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.9600.0 <6.3.9600.22371
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <10.0.17763.6775
Microsoft · Windows 11 Version 23H2version=10.0.22631.0 <10.0.22631.4751
Microsoft · Windows 11, version 22H2version=10.0.22621.0 <10.0.22621.4751
Microsoft · Windows 10 Version 1607version=10.0.14393.0 <10.0.14393.7699
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.3091
Microsoft · Windows Server 2025version=10.0.26100.0 <10.0.26100.2894
Microsoft · Windows 10 Version 1809version=10.0.17763.0 <10.0.17763.6775
Microsoft · Windows Server 2012 R2version=6.3.9600.0 <6.3.9600.22371

Published CVSS scores

6.5Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:N/UI:R/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 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 exploitUnconfirmed

Weakness, pattern, technique

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

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo