CVE-2024-56614: Linux Kernel Buffer Overflow Vulnerability

CVE-2024-56614 Overview

CVE-2024-56614 is an out-of-bounds write vulnerability in the Linux kernel's XSK (AF_XDP socket) map implementation. The vulnerability exists in the xsk_map_delete_elem function where an unsigned integer (map->max_entries) is compared with a user-controlled signed integer (k). Due to implicit type conversion during this comparison, a large unsigned value for map->max_entries can bypass the intended bounds check, allowing an attacker with local access to cause memory corruption.

Critical Impact

Local attackers with the ability to interact with BPF maps can exploit this vulnerability to achieve out-of-bounds memory writes, potentially leading to privilege escalation, kernel memory corruption, or system crashes.

Affected Products

• Linux Kernel (multiple versions prior to the security patches)
• Linux Kernel 6.13-rc1
• Systems using AF_XDP sockets and XSK map functionality

Discovery Timeline

• December 27, 2024 - CVE-2024-56614 published to NVD
• November 03, 2025 - Last updated in NVD database

Technical Details for CVE-2024-56614

Vulnerability Analysis

The vulnerability resides in the XSK map subsystem of the Linux kernel, specifically in the xsk_map_delete_elem function. This function is responsible for deleting elements from the XSK map, which is used by AF_XDP sockets for high-performance packet processing.

The core issue stems from a signed/unsigned integer comparison flaw. When the function performs a bounds check using if (k >= map->max_entries), the comparison between the unsigned map->max_entries and the signed k variable leads to implicit type conversion. This allows a user to supply a negative value for k (between -2147483648 and -2), which bypasses the bounds check entirely.

Once the bounds check is bypassed, the negative value is used as an array index in m->xsk_map[k], resulting in an out-of-bounds memory access. The subsequent xchg operation on this invalid memory location enables arbitrary memory writes, and the corrupted map_entry passed to xsk_map_sock_delete can cause additional memory corruption.

Root Cause

The root cause is a classic signed/unsigned integer comparison vulnerability (CWE-787: Out-of-bounds Write). The xsk_map_delete_elem function accepts a user-controlled signed integer key but compares it against an unsigned maximum entry count. C's implicit type conversion rules cause the signed value to be interpreted as unsigned during the comparison, allowing negative values to appear as very large positive numbers that may exceed max_entries, or in certain configurations, bypass the check entirely.

The vulnerable code path follows this sequence:

1. User supplies a negative key value through the BPF syscall
2. The bounds check fails to catch the invalid negative index
3. The negative index is used for array access, resulting in OOB access
4. The xchg operation writes to invalid kernel memory

Attack Vector

This is a local attack vector requiring the attacker to have access to the BPF syscall interface. The attack proceeds through the following mechanism:

The attacker interacts with an existing XSK map via the __sys_bpf syscall, specifically using the BPF_MAP_DELETE_ELEM command. By carefully crafting the key value as a negative signed integer, the attacker can cause the kernel to access memory outside the bounds of the xsk_map array.

The kernel crash log demonstrates the exploitation result, showing a page fault when attempting to write to address ffffc8fc2e461108. The call trace confirms the path through xsk_map_delete_elem to __sys_bpf and ultimately the userspace syscall entry point.

Detection Methods for CVE-2024-56614

Indicators of Compromise

• Unexpected kernel oops or panic messages referencing xsk_map_delete_elem in the call trace
• Page fault errors in kernel mode with addresses outside valid XSK map memory ranges
• Suspicious BPF syscall activity from unprivileged or unexpected processes
• System instability or crashes correlated with AF_XDP socket operations

Detection Strategies

• Monitor kernel logs (dmesg) for BUG or Oops messages containing references to xsk_map_delete_elem or XSK-related functions
• Implement syscall filtering to detect anomalous BPF map operations, particularly BPF_MAP_DELETE_ELEM commands with unusual key values
• Deploy kernel instrumentation or eBPF-based monitoring to track BPF map operations and flag suspicious patterns
• Use SentinelOne's Singularity platform to detect kernel-level exploitation attempts and anomalous system behavior

Monitoring Recommendations

• Enable kernel crash dump collection and analysis to capture exploitation attempts
• Configure audit logging for BPF syscall usage across the system
• Monitor for processes unexpectedly loading or interacting with XSK maps
• Implement runtime kernel integrity monitoring to detect memory corruption

How to Mitigate CVE-2024-56614

Immediate Actions Required

• Update affected Linux kernel installations to patched versions immediately
• Restrict access to the BPF syscall using seccomp filters or BPF permission controls where feasible
• Review and limit which users and processes can create or interact with XSK maps
• Consider disabling AF_XDP functionality if not required in production environments

Patch Information

The Linux kernel maintainers have released patches to address this vulnerability. The fix ensures proper signed/unsigned integer handling in the bounds check within xsk_map_delete_elem. Multiple commits have been applied to stable kernel branches:

• Kernel Git Commit 32cd3db
• Kernel Git Commit 4d03f70
• Kernel Git Commit d486b57
• Kernel Git Commit ed08c93
• Kernel Git Commit f8abd03

Debian has also released security updates as documented in their LTS Announcement.

Workarounds

• Restrict BPF syscall access using seccomp profiles to limit exposure to untrusted users
• Use kernel module parameters or boot options to disable XSK map functionality if not needed
• Implement network namespace isolation to limit access to AF_XDP socket interfaces
• Apply defense-in-depth controls including mandatory access control policies (SELinux/AppArmor) to restrict BPF operations

# Example: Restrict BPF capabilities using sysctl
# Limit unprivileged BPF access
echo 2 > /proc/sys/kernel/unprivileged_bpf_disabled

# Verify the setting
cat /proc/sys/kernel/unprivileged_bpf_disabled