CVE-2024-41009: Linux Kernel Privilege Escalation Flaw

CVE-2024-41009 Overview

A resource allocation vulnerability has been identified in the Linux kernel's BPF (Berkeley Packet Filter) ring buffer implementation. The vulnerability allows a local attacker with low privileges to cause a denial of service condition by exploiting improper handling of memory reservations in the circular buffer implementation. This flaw stems from insufficient validation when allocating memory chunks, potentially allowing overlapping memory regions that can corrupt internal data structures and cause system crashes.

Critical Impact

Local attackers can exploit this BPF ring buffer vulnerability to cause system crashes and denial of service by manipulating memory chunk allocations to overlap and corrupt internal headers.

Affected Products

• Linux Kernel (multiple versions)
• Debian Linux (affected via kernel packages)
• Systems running BPF programs with ring buffer maps

Discovery Timeline

• July 17, 2024 - CVE CVE-2024-41009 published to NVD
• November 3, 2025 - Last updated in NVD database

Technical Details for CVE-2024-41009

Vulnerability Analysis

The BPF ring buffer is implemented as a power-of-2 sized circular buffer that uses two logical counters: consumer_pos (tracking consumed data) and producer_pos (tracking reserved data by producers). A key optimization in the implementation maps the data area twice contiguously in virtual memory, eliminating the need for special handling when samples wrap around the buffer boundary.

The vulnerability exists in how memory reservations are validated. Each record contains a struct bpf_ringbuf_hdr with len and pg_off fields for bookkeeping. The flaw allows an attacker to manipulate the consumer_pos before calling bpf_ringbuf_reserve(), enabling the allocation of overlapping memory chunks.

In the demonstrated attack scenario with a BPF_MAP_TYPE_RINGBUF map of size 0x4000, an attacker can modify consumer_pos to 0x3000 before reserving memory. This allows chunk A to be allocated at [0x0,0x3008]. Subsequently, a second chunk B of size 0x3000 can be allocated at [0x3008,0x6010] because the manipulated consumer_pos bypasses the new_prod_pos - cons_pos > rb->mask validation check.

Due to the double-mapping of memory regions [0x0,0x4000] and [0x4000,0x8000] pointing to the same physical pages, chunk B at [0x4000,0x4008] directly overlaps with chunk A's header. When chunk B modifies this region and bpf_ringbuf_submit() or bpf_ringbuf_discard() is called, the corrupted pg_off value causes bpf_ringbuf_restore_from_rec() to reference an incorrect page, resulting in a system crash.

Root Cause

The root cause is insufficient validation of the relationship between consumer_pos and new producer reservations. The original implementation only checked if the new producer position exceeded the mask relative to the consumer position, but failed to account for scenarios where the consumer_pos could be manipulated from user space to create overlapping memory allocations spanning the ring buffer's wraparound boundary.

Attack Vector

The attack requires local access with low privileges to create and manipulate BPF ring buffer maps. The attacker must:

1. Create a BPF_MAP_TYPE_RINGBUF map with a known size
2. Manipulate the consumer_pos counter (accessible from user space as read-write)
3. Make strategic calls to bpf_ringbuf_reserve() to allocate overlapping chunks
4. Modify the overlapped header region through the second chunk
5. Trigger bpf_ringbuf_commit() to cause the crash via corrupted header data

The fix introduces validation by calculating the oldest pending_pos and checking whether the range from the oldest outstanding record to the newest would span beyond the ring buffer size, rejecting requests that would cause overlapping allocations.

Detection Methods for CVE-2024-41009

Indicators of Compromise

• Unexpected kernel crashes or panics related to BPF subsystem operations
• Anomalous BPF ring buffer map creation patterns with specific size values
• System logs showing errors in bpf_ringbuf_commit() or bpf_ringbuf_restore_from_rec() functions
• Unusual manipulation of BPF map consumer positions from user space processes

Detection Strategies

• Monitor for kernel oops or panics with stack traces involving bpf_ringbuf_* functions
• Implement audit logging for BPF map creation, particularly BPF_MAP_TYPE_RINGBUF types
• Deploy kernel integrity monitoring to detect exploitation attempts targeting BPF subsystems
• Use SentinelOne's behavioral AI to identify anomalous BPF program loading and execution patterns

Monitoring Recommendations

• Enable kernel tracing for BPF-related system calls using ftrace or perf
• Monitor /sys/kernel/debug/tracing for BPF ring buffer operations
• Implement alerting on kernel crash dumps mentioning ring buffer or BPF components
• Review system logs for repeated failed BPF operations that may indicate exploitation attempts

How to Mitigate CVE-2024-41009

Immediate Actions Required

• Update the Linux kernel to a patched version that includes the fix for CVE-2024-41009
• Review and restrict access to BPF functionality using kernel.unprivileged_bpf_disabled sysctl
• Monitor systems for signs of exploitation until patches can be applied
• Consider temporarily disabling BPF capabilities for unprivileged users in critical environments

Patch Information

The Linux kernel maintainers have released patches addressing this vulnerability. Multiple commits have been applied to stable kernel branches:

• Kernel Git Commit 47416c85
• Kernel Git Commit 511804ab
• Kernel Git Commit cfa1a232
• Kernel Git Commit d1b9df04

For Debian-based systems, refer to the Debian LTS Announcement for package updates.

Workarounds

• Restrict BPF access to privileged users only by setting sysctl kernel.unprivileged_bpf_disabled=1
• Implement mandatory access control policies (SELinux/AppArmor) to limit BPF system call access
• Use namespace isolation to restrict BPF capabilities in containerized environments
• Consider using seccomp filters to block BPF-related system calls for untrusted workloads

# Disable unprivileged BPF access
echo 1 > /proc/sys/kernel/unprivileged_bpf_disabled

# Make the setting persistent across reboots
echo "kernel.unprivileged_bpf_disabled = 1" >> /etc/sysctl.d/99-security.conf
sysctl -p /etc/sysctl.d/99-security.conf