CVE-2026-62757: Windows Schannel Security Feature Bypass Vulnerability

Overview

Severity

Medium (CVSS 5.3)

CVSS Vector

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

Category

Security Feature Bypass

Exploit Status

Not Exploited

Exploitation Likelihood

Unlikely

Patch Tuesday

2026-Aug

Released

2026-08-11

Description

Improper verification of cryptographic signature in Windows Schannel allows an unauthorized attacker to bypass a security feature over a network.

FAQ

What kind of security feature could be bypassed by successfully exploiting this vulnerability? An attacker who successfully exploited this vulnerability could bypass certificate validation during the account enrollment process. According to the CVSS metric, the attack complexity is high (AC:H). What does this mean for this vulnerability? An attacker would need specific conditions to be in place (i.e. particular protocol settings, or configurations, etc.) before an attack could succeed, which reduces the likelihood of widespread or opportunistic exploitation.

Affected Products (30)

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 25H2 for ARM64-based Systems
• Windows 11 Version 25H2 for x64-based Systems
• Windows 11 Version 23H2 for ARM64-based Systems
• Windows 11 Version 23H2 for x64-based Systems
• Windows 11 Version 24H2 for ARM64-based Systems
• Windows 11 Version 24H2 for x64-based Systems
• Windows Server 2025
• Windows 11 version 26H1 for x64-based Systems
• Windows 11 Version 26H1 for ARM64-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 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 2012
• Windows Server 2012 (Server Core installation)
• Windows Server 2012 R2
• Windows Server 2012 R2 (Server Core installation)

Security Updates (13)

• 5120238
• 5120242
• 5120229
• 5120249
• 5120233
• 5120228
• 5121003
• 5120994
• 5120240
• 5121000
• 5120418
• 5120385
• 5120386

Acknowledgments

Microsoft

Revision History

• 2026-08-11: Information published.