CVE-2023-1513

What it actually does

On 32-bit systems the KVM_GET_DEBUGREGS ioctl copies uninitialized portions of the kvm_debugregs structure from kernel memory to userspace, resulting in a limited information disclosure of kernel stack or register contents.

Why it matters to the business

Attackers with local access on affected 32-bit Linux systems can obtain small amounts of kernel memory that may contain sensitive values, increasing the chance of successful follow-on attacks and raising overall risk to systems running unpatched kernels.

How an attack unfolds

A local attacker obtains a file descriptor to /dev/kvm, issues the KVM_GET_DEBUGREGS ioctl on a 32-bit KVM virtual machine, and receives a structure containing leftover kernel data in the uninitialized fields, which can be inspected for useful values such as pointers or credentials.

How to fix it

Upgrade the Linux kernel to a version containing commit c9c3395d5e3dcc6daee66c6908354d47bf98cb0c or later; rebuild and reboot all affected 32-bit systems; disable KVM on 32-bit hosts if the feature is not required.

How to confirm the fix worked

Confirm the running kernel contains commit c9c3395d5e3dcc6daee66c6908354d47bf98cb0c or a later equivalent; verify that KVM_GET_DEBUGREGS no longer returns uninitialized bytes by comparing multiple ioctl results on a test system.

Typical attack path

1. Obtain local shell or process on a 32-bit Linux host with KVM enabled
2. Open /dev/kvm and create or attach to a virtual machine
3. Call the KVM_GET_DEBUGREGS ioctl and receive the partially uninitialized structure
4. Parse returned data for kernel pointers or other sensitive values to aid further exploitation

How to detect it

Review authentication and process-creation logs for unexpected local access to KVM devices; examine any recorded ioctl calls involving KVM_GET_DEBUGREGS; look for post-exploitation activity that follows kernel-memory disclosure patterns such as credential dumping or pointer leaks.

What your security team should do

• Prioritize patching all 32-bit Linux KVM hosts within standard change windows
• Audit inventories for any remaining 32-bit systems running KVM and schedule decommissioning or upgrade
• Add kernel version checks to vulnerability scanning policies