CVE-2026-62779 Overview
CVE-2026-62779 is a use-after-free vulnerability [CWE-416] in the Windows Secure Channel (Schannel) component. Schannel implements Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols on Windows platforms. An authorized local attacker can exploit this flaw to elevate privileges on affected systems. Microsoft published the advisory on August 11, 2026, covering Windows 11 versions 24H2, 25H2, 26H1, and Windows Server 2025 across x64 and ARM64 architectures.
Critical Impact
A local attacker with low-privileged authenticated access can execute code with elevated privileges, compromising confidentiality, integrity, and availability of the host.
Affected Products
- Microsoft Windows 11 24H2 (x64, ARM64)
- Microsoft Windows 11 25H2 (x64, ARM64)
- Microsoft Windows 11 26H1 (x64, ARM64)
- Microsoft Windows Server 2025 (x64)
Discovery Timeline
- 2026-08-11 - CVE-2026-62779 published to NVD
- 2026-08-13 - Last updated in NVD database
Technical Details for CVE-2026-62779
Vulnerability Analysis
The vulnerability resides in Windows Schannel, the Security Support Provider (SSP) that handles TLS/SSL cryptographic operations on Windows. Schannel manages security contexts, credential handles, and session state on behalf of applications performing secure communication. A use-after-free condition arises when the component references a memory object after it has been freed.
An authenticated attacker running low-privileged code on the target host can trigger the flawed code path and manipulate the freed allocation. Successful exploitation permits execution in the context of a higher-privileged process that consumes Schannel, resulting in local privilege escalation. The vulnerability affects confidentiality, integrity, and availability at the host level.
Root Cause
The root cause is improper object lifetime management within Schannel. A pointer to a heap-allocated object continues to be used after the object memory has been released. When the attacker reclaims that memory with attacker-controlled data before the dangling pointer is dereferenced, control-flow or data-flow corruption occurs inside a privileged process.
Attack Vector
Exploitation requires local access and existing low-privileged authentication on the target system. No user interaction is required. The attacker interacts with Schannel through supported API surfaces such as AcquireCredentialsHandle, InitializeSecurityContext, or related SSPI calls to reach the vulnerable free-and-reuse path. Refer to the Microsoft CVE-2026-62779 Advisory for vendor guidance.
Detection Methods for CVE-2026-62779
Indicators of Compromise
- Unexpected crashes or exceptions in processes hosting Schannel, such as lsass.exe, with access violations referencing freed heap memory.
- New privileged processes or tokens spawned from a low-privileged user session shortly after Schannel API activity.
- Windows Error Reporting entries citing faulting module schannel.dll on unpatched hosts.
Detection Strategies
- Monitor for anomalous token duplication or impersonation events (Event IDs 4624 type 9, 4672) originating from standard user contexts.
- Alert on process integrity level transitions where a Medium-integrity process suddenly gains SYSTEM privileges.
- Correlate Schannel API usage patterns with subsequent privilege changes on the same host.
Monitoring Recommendations
- Enable kernel-mode and userland exploit protection telemetry on Windows 11 24H2/25H2/26H1 and Windows Server 2025 endpoints.
- Ingest Sysmon Event ID 10 (ProcessAccess) targeting lsass.exe and other Schannel consumers into your SIEM.
- Track patch compliance status for the August 2026 Microsoft security update across all affected SKUs.
How to Mitigate CVE-2026-62779
Immediate Actions Required
- Apply the August 2026 Microsoft security update to all Windows 11 24H2, 25H2, 26H1, and Windows Server 2025 systems.
- Inventory affected hosts using CPE identifiers and prioritize patching of servers exposing authenticated services.
- Restrict local interactive and remote interactive logon rights to reduce the pool of accounts that can trigger the flaw.
Patch Information
Microsoft has released a security update addressing CVE-2026-62779. Consult the Microsoft CVE-2026-62779 Advisory for the specific KB article numbers and package downloads corresponding to each affected build.
Workarounds
- No official workaround has been published by Microsoft; patching is the required remediation.
- Enforce least privilege and remove standing local administrator rights to limit the attacker foothold required for exploitation.
- Apply application control policies such as Windows Defender Application Control (WDAC) to block unauthorized binaries from executing on affected hosts.
# Verify patch status on Windows using PowerShell
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
