CVE-2021-26708

What it actually does

Race conditions in the AF_VSOCK implementation caused by incorrect locking in net/vmw_vsock/af_vsock.c allow a local attacker to escalate privileges.

Why it matters to the business

Attackers with local access can gain full root control of affected Linux systems, enabling data theft, persistence, or disruption of operations.

How an attack unfolds

A local attacker triggers multiple race conditions in VSOCK multi-transport support to overwrite kernel structures and escalate from unprivileged access to root.

How to fix it

Upgrade the Linux kernel to version 5.10.13 or newer, incorporating commit c518adafa39f37858697ac9309c6cf1805581446 from the mainline repository.

How to confirm the fix worked

Confirm the running kernel version is 5.10.13 or later and verify the presence of the locking fixes in net/vmw_vsock/af_vsock.c.

Typical attack path

1. Gain local shell or process execution on the target system
2. Trigger concurrent operations on AF_VSOCK sockets to hit the locking races
3. Overwrite kernel memory or credentials to obtain root privileges
4. Execute arbitrary code or maintain access with elevated rights

How to detect it

Review kernel logs and audit trails for vsock socket activity coinciding with unexpected privilege changes or process escalations.

What your security team should do

• Apply the kernel update to all affected systems as soon as possible
• Limit local user accounts and enforce least-privilege access
• Monitor kernel logs for vsock-related anomalies or crashes