CVE-2024-50264: Linux Kernel Use-After-Free Vulnerability

CVE-2024-50264 Overview

CVE-2024-50264 is a Use-After-Free vulnerability in the Linux kernel's vsock/virtio subsystem. The vulnerability occurs during loopback communication when a dangling pointer is created in vsk->trans, which can potentially be exploited to achieve arbitrary code execution or cause system instability. This issue affects the virtual socket (vsock) implementation used for communication between virtual machines and their hypervisors.

Critical Impact

Local attackers with low privileges can exploit this Use-After-Free condition to potentially execute arbitrary code with elevated privileges, compromise system integrity, or cause denial of service conditions on affected Linux systems.

Affected Products

• Linux Kernel versions prior to the security patches
• Linux Kernel 6.12 release candidates (rc1 through rc6)
• Multiple stable kernel branches requiring backported fixes

Discovery Timeline

• 2024-11-19 - CVE-2024-50264 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2024-50264

Vulnerability Analysis

The vulnerability resides in the virtio transport layer of the Linux kernel's vsock (virtual socket) implementation. During loopback communication scenarios, the vsk->trans pointer can become a dangling pointer—a pointer that references memory that has already been freed. When this freed memory is subsequently accessed through the dangling pointer, it creates a classic Use-After-Free condition.

The vsock subsystem provides socket-based communication between virtual machines and the host system, making this vulnerability particularly relevant in virtualized environments. The Use-After-Free condition can lead to memory corruption, allowing an attacker to potentially control program execution flow or leak sensitive kernel memory.

Root Cause

The root cause of this vulnerability is improper pointer initialization in the vsock virtio transport code. Specifically, the vsk->trans pointer was not being initialized to NULL, allowing it to retain stale memory addresses after the associated memory was freed. This dangling pointer scenario occurs during loopback communication when transport structures are allocated and deallocated.

The fix addresses this by ensuring vsk->trans is properly initialized to NULL, preventing the dangling pointer condition from occurring.

Attack Vector

This vulnerability requires local access to the system with low privileges. An attacker can exploit this vulnerability by initiating loopback vsock communication in a way that triggers the Use-After-Free condition. The attack does not require user interaction and can potentially be exploited through applications that utilize the vsock interface for inter-VM communication.

The exploitation of Use-After-Free vulnerabilities typically involves manipulating heap memory allocation to place attacker-controlled data in the freed memory region. When the dangling pointer is dereferenced, the attacker's data is accessed instead of the legitimate transport structure, potentially allowing arbitrary code execution with kernel privileges.

Detection Methods for CVE-2024-50264

Indicators of Compromise

• Kernel crash logs or oops messages referencing vsock or virtio transport code paths
• Unexpected memory corruption errors in kernel logs related to vsk->trans structures
• Anomalous vsock loopback activity patterns on systems that should not be using this functionality

Detection Strategies

• Enable kernel debugging options such as KASAN (Kernel Address Sanitizer) to detect Use-After-Free accesses
• Monitor for unexpected vsock socket creation and loopback communication attempts
• Implement system call auditing to track vsock-related operations from unprivileged processes

Monitoring Recommendations

• Deploy SentinelOne Singularity Platform for real-time kernel-level threat detection and behavioral analysis
• Configure kernel audit rules to log vsock-related system calls and socket operations
• Monitor system stability indicators and kernel crash reports for patterns matching this vulnerability

How to Mitigate CVE-2024-50264

Immediate Actions Required

• Update the Linux kernel to a patched version from your distribution vendor
• Review Debian LTS security announcements for applicable patches: Debian LTS Announcement January 2025 and Debian LTS Announcement March 2025
• Prioritize patching systems running virtualized workloads or container environments where vsock is actively used

Patch Information

Multiple kernel patches have been released to address this vulnerability across different kernel branches. The fix initializes vsk->trans to NULL to prevent the dangling pointer condition. Key patches are available through the official kernel git repository:

• Kernel Git Commit #2a6a4e69
• Kernel Git Commit #44d29897
• Kernel Git Commit #5f092a42
• Kernel Git Commit #6ca57537
• Kernel Git Commit #b110196fe
• Kernel Git Commit #eb1bdcb7
• Kernel Git Commit #fd8ae346

For detailed technical analysis of the vulnerability and exploitation techniques, refer to the GitHub CVE-2024-50264 Analysis.

Workarounds

• Disable or restrict vsock functionality if not required by removing the vsock and virtio_transport kernel modules: modprobe -r vsock_loopback virtio_transport vsock
• Implement access controls to limit which users and processes can create vsock sockets
• Use kernel security modules (SELinux, AppArmor) to restrict vsock socket operations to authorized applications only

# Disable vsock modules if not required
echo "blacklist vsock_loopback" >> /etc/modprobe.d/vsock-disable.conf
echo "blacklist virtio_transport" >> /etc/modprobe.d/vsock-disable.conf
echo "blacklist vsock" >> /etc/modprobe.d/vsock-disable.conf

# Apply changes without reboot (if modules are not in use)
modprobe -r vsock_loopback virtio_transport vsock 2>/dev/null || echo "Modules may be in use, reboot required"