CVE-2024-33619

What it actually does

In the Linux kernel EFI stub, priv.runtime_map is freed unconditionally in an error path even when efi_novamap is set and the pointer remains uninitialized, resulting in an invalid free_pool call and potential memory corruption or kernel panic.

Why it matters to the business

May cause Linux systems to crash or become unstable during boot on EFI platforms, leading to denial of service and operational downtime; low prevalence of active exploitation reduces immediate risk across the ecosystem.

How an attack unfolds

A local attacker triggers EFI stub initialization with efi_novamap enabled, forces an error path, and causes the kernel to attempt freeing an uninitialized pointer, resulting in a crash; no remote or code-execution paths are known.

How to fix it

Upgrade the Linux kernel to the fixed commit b8938d6f570f010a1dcdbfed3e5b5d3258c2a908 or apply the equivalent stable patch that adds the allocation check before freeing runtime_map.

How to confirm the fix worked

Inspect the efi-stub source for a conditional free of runtime_map based on whether it was allocated; verify the running kernel contains commit b8938d6f570f010a1dcdbfed3e5b5d3258c2a908 or later.

Typical attack path

1. Set efi_novamap kernel parameter or equivalent EFI configuration
2. Initiate boot or EFI runtime map allocation path
3. Induce an error condition that reaches the unconditional free_pool call
4. Trigger kernel panic or undefined behavior from invalid pointer free

How to detect it

Review kernel logs for EFI stub error paths or panics mentioning runtime_map or free_pool; no widespread exploitation indicators have been observed.

What your security team should do

• Apply the referenced kernel commit or newer stable release to all affected systems
• Prioritize patching EFI-enabled Linux hosts in the next maintenance window
• Monitor upstream stable kernel updates for any follow-on EFI stub fixes