EUVD-2026-44245
GHSA-9hmw-8q29-cpgf
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Network-reachable, low-complexity, authenticated (PR:L) over-read yielding high confidentiality loss; I:N and A:N since the description confirms only information disclosure, not integrity or availability impact.
Primary rating from Vendor (microsoft).
CVSS VectorNVD
Lifecycle Timeline
4DescriptionNVD
Out-of-bounds read in Windows Schannel allows an authorized attacker to disclose information over a network.
AnalysisAI
Information disclosure in Microsoft Windows Schannel (the Secure Channel TLS/SSL provider) lets an authenticated, network-adjacent attacker read memory beyond an allocated buffer and leak sensitive data across a network connection. The flaw spans nearly the entire supported Windows family - Windows 10 (1607 through 22H2), Windows 11 (24H2/25H2/26H1), and Windows Server 2012 through 2025. Reported by Microsoft with a fix available; there is no public exploit identified at time of analysis, and it is not listed in CISA KEV.
Technical ContextAI
Schannel (Secure Channel) is the Windows implementation of the TLS/SSL and DTLS protocols, used by IIS, RDP, LDAPS, SMB over TLS, and virtually every Windows service that negotiates encrypted sessions. The root cause is CWE-125 (Out-of-bounds Read): during processing of protocol data, the component reads past the bounds of an allocated buffer, allowing adjacent process memory to be returned to the peer. Because Schannel handles attacker-influenced handshake and record data, malformed or crafted TLS structures can drive the parser to over-read. The CPE set confirms the affected code is the OS-level Schannel component shipped uniformly across Windows 10, Windows 11, and Windows Server 2012-2025.
RemediationAI
Apply the Microsoft security update for your specific Windows build - Patch available per vendor advisory; consult https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56186 for the exact patched KB and build number for each affected SKU (exact fix version is not restated in the provided data, so pull it from MSRC per your OS). Since the flaw is in the core TLS provider, patching is the only complete fix; there is no supported feature toggle to disable Schannel. As interim compensating controls until patching, restrict network reachability of TLS-terminating services (IIS, RDP, LDAPS, SMB-over-TLS) to trusted management networks and enforce the PR:L barrier by tightening authentication, since exploitation requires an authenticated/authorized attacker - the trade-off is reduced service accessibility for legitimate remote clients. Prioritize internet-exposed and multi-tenant servers first.
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Same weakness CWE-125 – Out-of-bounds Read
View allSame technique Buffer Overflow
View allShare
External POC / Exploit Code
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