Description

Use after free in Windows Schannel allows an authorized attacker to elevate privileges locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-11T17:18:31.153Z",
  "pubdate": "2026-08-11T17:18:31.153Z",
  "executiveSummary": "This vulnerability is classified as a use-after-free weakness affecting the Windows Schannel security package. The primary impact of successful exploitation is local privilege escalation, allowing an authorized adversary to execute arbitrary code with elevated privileges on the targeted system.\nThe affected product is Windows Schannel, a security support provider that implements Secure Sockets Layer and Transport Layer Security protocols. The risk implications are severe, as compromise of local administrative or system-level privileges typically leads to full host takeover, lateral movement across the enterprise network, and complete bypass of operating system security boundaries.\nAttacker capabilities require local access to the system with authorization. Exploitation prerequisites mandate that the attacker has already obtained initial execution capabilities within the local environment and can interact with the vulnerable Schannel component to trigger memory corruption conditions.",
  "technicalDetails": "The root cause of the vulnerability stems from improper memory management within the Windows Schannel component during the handling of cryptographic context and connection state objects. Specifically, a use-after-free condition occurs when an object is prematurely freed or deallocated while references to it still exist within internal control blocks or request queues.\nThe vulnerable component resides within the Schannel subsystem responsible for managing secure communication sessions and protocol handshakes. When an authorized process interacts with the affected component, improper synchronization or error handling leads to the dangling pointer scenario.\nThe attack flow begins when an attacker with local execution privileges crafts specific API requests or session manipulation sequences directed at Schannel. The attacker forces the targeted object to be released while maintaining a secondary reference. By subsequently allocating controlled data into the recently freed memory location (heap spraying or grooming), the attacker achieves deterministic memory corruption.\nWhen the Schannel subsystem attempts to reference the dangling pointer, it processes attacker-controlled data as legitimate internal control structures or function pointers. This memory manipulation allows the execution of arbitrary instructions within the context of a privileged system process.\nAuthentication requirements dictate that the attacker must be locally authenticated to the operating system. Privilege requirements involve executing the initial payload from a low-privileged context to target the local privilege escalation vector. Network exposure is localized, as the vulnerability requires local interaction with the Windows Schannel interfaces rather than direct remote exploitation over external network boundaries."
}