CVE-2024-25744: Linux Kernel Privilege Escalation Flaw

CVE-2024-25744 Overview

CVE-2024-25744 is a kernel vulnerability in the Linux kernel before version 6.6.7 that allows an untrusted Virtual Machine Monitor (VMM) to trigger int80 syscall handling at any given point. This vulnerability affects the confidential computing components, specifically the Intel TDX (Trust Domain Extensions) and AMD SEV (Secure Encrypted Virtualization) implementations found in arch/x86/coco/tdx/tdx.c and arch/x86/mm/mem_encrypt_amd.c.

Critical Impact

An untrusted VMM can manipulate int80 syscall handling to potentially compromise the confidentiality, integrity, and availability of protected virtual machines in confidential computing environments.

Affected Products

• Linux Kernel versions prior to 6.6.7
• Systems utilizing Intel TDX (Trust Domain Extensions)
• Systems utilizing AMD SEV (Secure Encrypted Virtualization)

Discovery Timeline

• 2024-02-12 - CVE-2024-25744 published to NVD
• 2025-05-07 - Last updated in NVD database

Technical Details for CVE-2024-25744

Vulnerability Analysis

This vulnerability exists in the Linux kernel's confidential computing subsystem, specifically affecting the handling of legacy int80 syscalls within Intel TDX and AMD SEV protected environments. In confidential computing scenarios, the VMM (hypervisor) is considered untrusted, and the guest operating system must be protected from malicious VMM actions.

The vulnerability allows an untrusted VMM to inject int80 syscall events into the guest at arbitrary points during execution. This breaks the security model of confidential computing where the guest should be isolated from VMM manipulation. The int80 instruction is a legacy 32-bit syscall mechanism that, when triggered unexpectedly, can disrupt the normal execution flow of the protected guest operating system.

The affected code paths are located in:

• arch/x86/coco/tdx/tdx.c - Intel Trust Domain Extensions handling
• arch/x86/mm/mem_encrypt_amd.c - AMD Secure Encrypted Virtualization memory encryption

Root Cause

The root cause of this vulnerability is the insufficient validation of VMM-injected events in the confidential computing exception handlers. The kernel did not properly validate or restrict the circumstances under which int80 syscalls could be triggered, allowing an untrusted VMM to inject these events at arbitrary points in guest execution. This represents a Protection Mechanism Failure (CWE-693) where the security controls intended to isolate the guest from the untrusted VMM were inadequate.

Attack Vector

The attack requires local access where an attacker with control over the VMM can target protected guest virtual machines. The attacker can inject int80 syscall events into the guest at arbitrary execution points, potentially leading to:

• Disruption of guest execution flow
• Information disclosure from the protected guest
• Potential privilege escalation within the guest context
• Compromise of the confidentiality guarantees provided by TDX/SEV

The attack does not require user interaction and can be performed with low privileges on the host system, though the scope extends beyond the vulnerable component to affect the protected guest environment.

Detection Methods for CVE-2024-25744

Indicators of Compromise

• Unexpected int80 syscall activity logged in protected guest environments
• Anomalous VMM behavior patterns targeting TDX or SEV protected guests
• Unusual exception handling activity in confidential computing workloads
• System instability or crashes in protected virtual machines

Detection Strategies

• Monitor kernel logs for unexpected syscall injection attempts in confidential computing environments
• Implement runtime integrity monitoring for TDX and SEV protected guests
• Deploy kernel-level auditing to track int80 syscall invocations in protected contexts
• Use SentinelOne Singularity Platform to detect anomalous kernel-level activity and VMM manipulation attempts

Monitoring Recommendations

• Enable verbose logging for confidential computing subsystems during security assessments
• Implement continuous monitoring of guest VM behavior for signs of VMM manipulation
• Deploy endpoint detection and response (EDR) solutions capable of monitoring kernel-level events
• Establish baseline behavior profiles for protected workloads to detect deviations

How to Mitigate CVE-2024-25744

Immediate Actions Required

• Update Linux kernel to version 6.6.7 or later immediately on all affected systems
• Review and audit all confidential computing deployments using TDX or SEV technologies
• Assess VMM trust boundaries and implement additional isolation measures where possible
• Monitor Linux Kernel Security Advisories for related patches

Patch Information

The vulnerability has been addressed in Linux kernel version 6.6.7. The fix is available in the Linux Kernel Commit b82a8db. Organizations running affected versions should prioritize upgrading to the patched kernel version. Additional advisory information is available from NetApp Security Advisory NTAP-20241115-0006.

Workarounds

• If immediate patching is not possible, consider isolating confidential computing workloads from untrusted VMM environments
• Implement additional monitoring and alerting for TDX/SEV protected guest environments
• Review and restrict access to VMM/hypervisor management interfaces
• Consider deploying workloads on patched infrastructure while legacy systems are updated

# Check current kernel version
uname -r

# Update kernel on Debian/Ubuntu systems
sudo apt update && sudo apt install linux-image-generic

# Update kernel on RHEL/CentOS systems
sudo yum update kernel

# Verify kernel version after update
uname -r