CVE-2025-21221: Windows Telephony Service Remote Code Execution Vulnerability

Overview

Severity

High (CVSS 8.8)

CVSS Vector

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

Category

Remote Code Execution

Exploit Status

Not Exploited

Exploitation Likelihood

Less Likely

Patch Tuesday

2025-Apr

Released

2025-04-08

Last Updated

2025-04-09

EPSS Score

1.10% (percentile: 78.1%)

Description

Heap-based buffer overflow in Windows Telephony Service allows an unauthorized attacker to execute code over a network.

FAQ

Are the updates for Windows 10 for x64-based Systems and Windows 10 for 32-bit Systems currently available? Yes. As of April 9, 2025, the security update (5055547) for Windows 10 for x64-based Systems and Windows 10 for 32-bit Systems are available. Customers running Windows 10 should ensure the update is installed to be protected from this vulnerability. According to the CVSS metric, the attack vector is network (AV:N) and the user interaction is required (UI:R). What is the target context of the remote code execution? This attack requires a client to connect to a malicious server, and that could allow the attacker to gain code execution on the client.

Affected Products (37)

Windows

• Windows 10 Version 1809 for 32-bit Systems
• Windows 10 Version 1809 for x64-based Systems
• Windows Server 2019
• Windows Server 2019 (Server Core installation)
• Windows Server 2022
• Windows Server 2022 (Server Core installation)
• Windows 10 Version 21H2 for 32-bit Systems
• Windows 10 Version 21H2 for ARM64-based Systems
• Windows 10 Version 21H2 for x64-based Systems
• Windows Server 2025 (Server Core installation)
• Windows 11 Version 23H2 for ARM64-based Systems
• Windows 11 Version 23H2 for x64-based Systems
• Windows Server 2022, 23H2 Edition (Server Core installation)
• Windows 11 Version 24H2 for ARM64-based Systems
• Windows 11 Version 24H2 for x64-based Systems
• Windows Server 2025
• Windows 10 for 32-bit Systems
• Windows 10 for x64-based Systems
• Windows 10 Version 1607 for 32-bit Systems
• Windows 10 Version 1607 for x64-based Systems
• Windows Server 2016
• Windows Server 2016 (Server Core installation)

ESU

• Windows 11 Version 22H2 for ARM64-based Systems
• Windows 11 Version 22H2 for x64-based Systems
• Windows 10 Version 22H2 for x64-based Systems
• Windows 10 Version 22H2 for ARM64-based Systems
• Windows 10 Version 22H2 for 32-bit Systems
• Windows Server 2008 for 32-bit Systems Service Pack 2
• Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation)
• Windows Server 2008 for x64-based Systems Service Pack 2
• Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation)
• Windows Server 2008 R2 for x64-based Systems Service Pack 1
• Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation)
• Windows Server 2012
• Windows Server 2012 (Server Core installation)
• Windows Server 2012 R2
• Windows Server 2012 R2 (Server Core installation)

Security Updates (14)

• 5055519
• 5055526
• 5055518
• 5055528
• 5055523
• 5055527
• 5055547
• 5055521
• 5055609
• 5055596
• 5055561
• 5055570
• 5055581
• 5055557

Acknowledgments

Floriel (EPIN)

Revision History

• 2025-04-08: Information published.
• 2025-04-09: The security updates for Windows 10 for 32-bit Systems and Windows 10 for x64-based Systems are now available. See the Security Updates table for more information.