Advisory · CVE-2026-97816
Use-after-free in OpenSSH for Windows allows unauthenticated code execution
OpenSSH for Windows has a use-after-free flaw an unauthenticated attacker can trigger over the network to execute code. Microsoft rates it CVSS 3.1 9.8.
- Vendor
- Microsoft
- Product
- OpenSSH for Windows
- Identifier / CWE
- CVE-2026-97816
CWE-416 - Action timing
- Immediate
Explain it like I’m five
The remote-access door itself has the flaw: the SSH service keeps using freed memory, and a connecting stranger can turn that into code execution before ever logging in.
- 01Reach the component
An unauthenticated attacker sends crafted network traffic to a Windows system running OpenSSH for Windows.
- 02Memory flaw triggers
The component mishandles the input and corrupts or reuses memory outside its intended bounds.
- 03Code runs
The attacker gains code execution in the component's context on the target system.
What happened
Microsoft disclosed CVE-2026-97816 in its October 2026 update guide: a use-after-free weakness (CWE-416) in OpenSSH for Windows lets an unauthorized attacker execute code over a network.
Microsoft lists the affected Windows releases in its update guide. Apply the October 2026 security updates for your release rather than relying on a version guess here.
What to do
- Inventory every OpenSSH for Windows deployment, including test, training, and individually managed instances.
- Apply the vendor fix or upgrade exactly as directed in the linked vendor bulletin or advisory.
- Restrict network access to OpenSSH for Windows while remediation is underway, especially for internet-facing instances.
- Review application and server logs for SSH service crashes, failed-connection floods, and successful logins from unfamiliar sources after instability.
- Check for accounts, content, or configuration created outside normal change processes, and rotate exposed credentials where access cannot be ruled out.
- Verify the deployed version or patch level after remediation.
Management note
An unauthenticated flaw in the remote administration service is as critical as it sounds. Patch SSH-exposed Windows hosts first and review authentication logs.