CVE-2024-36971: Linux Kernel Use-After-Free Vulnerability

CVE-2024-36971 Overview

In the Linux kernel, a vulnerability existed in the __dst_negative_advice() function, which did not enforce proper RCU (Read-Copy-Update) rules for clearing sk->dst_cache. This led to potential use-after-free (UAF) conditions, which could be exploited, especially when using UDP sockets.

Critical Impact

This vulnerability could allow local attackers to execute arbitrary code, compromising system integrity and availability.

Affected Products

• debian debian_linux
• linux linux_kernel

Discovery Timeline

• Not Available - Vulnerability discovered by Clement Lecigne
• Not Available - Responsible disclosure to debian
• Not Available - CVE CVE-2024-36971 assigned
• Not Available - debian releases security patch
• 2024-06-10 - CVE CVE-2024-36971 published to NVD
• 2025-11-05 - Last updated in NVD database

Technical Details for CVE-2024-36971

Vulnerability Analysis

The function __dst_negative_advice() was found to violate RCU rules, specifically in the sequence of clearing the sk_dst_cache. This improper sequence could lead to a use-after-free condition, where stale pointers are dereferenced, causing potential system crashes or further exploitation opportunities.

Root Cause

The root cause of this vulnerability was the incorrect ordering of operations in __dst_negative_advice(), where sk_dst_reset(sk) needed to be called before releasing the old dst entry.

Attack Vector

This is a local vulnerability, meaning that an attacker needs to have local access to the affected system to exploit it, typically via crafted UDP socket interactions.

// Example exploitation code (sanitized)
if (udp_socket) {
    sk_dst_reset(udp_socket);
    dst_release(old_dst);
}

Detection Methods for CVE-2024-36971

Indicators of Compromise

• Unexpected crashes related to UDP socket operations
• Kernel log entries indicating use-after-free conditions

Detection Strategies

Detection should focus on monitoring kernel logs for any anomalies during socket operations, especially looking for use-after-free indications.

Monitoring Recommendations

Utilize kernel debugging tools to trace RCU violations and socket operations. Regular audits of logs for anomalies related to UDP traffic are recommended.

How to Mitigate CVE-2024-36971

Immediate Actions Required

• Apply kernel patches immediately
• Audit current systems for indications of compromise
• Monitor for ongoing exploit attempts

Patch Information

For the complete patch and update procedures, refer to the official kernel patch link: Patch Link

Workarounds

No effective workarounds are known other than applying the patch.

# Configuration example
# To apply the patch, execute the following in your kernel source directory
patch -p1 < /path/to/patch
make
make modules_install
make install
reboot