Summary
Impact: Remote Code Execution. Microsoft rating: Critical. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
According to the CVSS metric, the attack complexity is high (AC:H). What does that mean for this vulnerability?
Successful exploitation of this vulnerability requires an attacker to send a large number of messages.
How could an attacker exploit the vulnerability?
An attacker can exploit this vulnerability by sending malicious fragmented ClientHello messages to a target server that accepts Transport Layer Security (TLS) connections.
Security updates
10.0.20348.3807 — https://support.microsoft.com/help/5060526
10.0.20348.3745 — https://support.microsoft.com/help/5060525
10.0.22621.5472 — https://support.microsoft.com/help/5060999
10.0.26100.4349 — https://support.microsoft.com/help/5060842
10.0.26100.4270 — https://support.microsoft.com/help/5060841
10.0.25398.1665 — https://support.microsoft.com/help/5060118
Vulnerabilities 1
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High 8.1
Windows Schannel Remote Code Execution Vulnerability
Missing release of memory after effective lifetime in Windows Cryptographic Services allows an unauthorized attacker to execute code over a network.
Revision history
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#1
Information published.
References
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CVE-2025-29828 Windows Schannel Remote Code Execution Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-29828
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Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
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Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
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Common Vulnerability Scoring System
https://www.first.org/cvss