CVE-2022-0264: Linux Kernel eBPF Information Disclosure

CVE-2022-0264 Overview

A vulnerability was found in the Linux kernel's eBPF verifier when handling internal data structures. Internal memory locations could be returned to userspace, allowing a local attacker with the permissions to insert eBPF code to the kernel to leak internal kernel memory details. This memory information disclosure flaw defeats some of the exploit mitigations in place for the kernel, potentially enabling further exploitation.

Critical Impact

Local attackers can leverage this eBPF verifier flaw to leak sensitive kernel memory information, potentially bypassing kernel exploit mitigations such as KASLR (Kernel Address Space Layout Randomization).

Affected Products

• Linux Kernel versions prior to v5.16-rc6
• Linux Kernel 5.16 (all release candidates through rc5)
• Linux Kernel 5.16-rc1 through 5.16-rc5

Discovery Timeline

• February 4, 2022 - CVE-2022-0264 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-0264

Vulnerability Analysis

This vulnerability resides in the Linux kernel's extended Berkeley Packet Filter (eBPF) verifier component. The eBPF subsystem is designed to allow userspace programs to run sandboxed code within the kernel for performance-critical tasks like packet filtering and system tracing. The verifier is responsible for ensuring that eBPF programs are safe to execute and cannot access arbitrary kernel memory.

The flaw occurs when the verifier improperly handles internal data structures, resulting in internal kernel memory locations being exposed to userspace. This constitutes a significant information disclosure vulnerability that undermines kernel security mechanisms designed to prevent exploitation.

Root Cause

The root cause is classified as CWE-755 (Improper Handling of Exceptional Conditions). The eBPF verifier fails to properly handle certain internal data structures, inadvertently allowing references to internal kernel memory addresses to be returned to userspace programs. This improper exception handling creates a pathway for information leakage that should never occur in normal eBPF operation.

Attack Vector

The attack requires local access to the system with permissions to load eBPF programs into the kernel. An attacker would craft a malicious eBPF program designed to trigger the improper handling condition in the verifier, causing internal memory addresses to be leaked. This information can then be used to:

1. Defeat Kernel Address Space Layout Randomization (KASLR)
2. Map kernel memory layout for subsequent exploitation
3. Identify locations of sensitive kernel structures
4. Facilitate more sophisticated kernel exploitation chains

The vulnerability requires unprivileged user access with CAP_BPF or CAP_SYS_ADMIN capabilities, or systems where unprivileged eBPF is enabled. The attacker submits specially crafted eBPF bytecode through the bpf() syscall, and the vulnerable verifier processes this code in a way that exposes internal memory references.

Detection Methods for CVE-2022-0264

Indicators of Compromise

• Unusual or unexpected eBPF program loading activity from non-administrative users
• Suspicious bpf() syscall patterns, particularly from processes that don't typically use eBPF
• Anomalous access to /sys/kernel/debug/tracing/ or BPF-related kernel interfaces
• Processes attempting to read kernel memory information after eBPF program execution

Detection Strategies

• Monitor bpf() syscall usage through audit logging with auditd rules targeting BPF operations
• Deploy kernel-level monitoring for eBPF program verification failures or unusual verifier behavior
• Implement SentinelOne's behavioral AI to detect exploitation patterns targeting kernel subsystems
• Track processes with CAP_BPF or CAP_SYS_ADMIN capabilities for suspicious activity

Monitoring Recommendations

• Enable kernel audit logging for BPF-related syscalls using auditctl -a always,exit -F arch=b64 -S bpf
• Monitor syslog and dmesg for eBPF verifier warnings or errors
• Implement file integrity monitoring on critical kernel-related paths
• Use SentinelOne Singularity platform for real-time kernel-level threat detection

How to Mitigate CVE-2022-0264

Immediate Actions Required

• Upgrade Linux kernel to version 5.16-rc6 or later to receive the security fix
• Disable unprivileged eBPF access by setting kernel.unprivileged_bpf_disabled=1 sysctl parameter
• Review and restrict user permissions for eBPF program loading (CAP_BPF, CAP_SYS_ADMIN)
• Apply vendor-specific patches from your Linux distribution

Patch Information

The vulnerability was addressed in Linux kernel version 5.16-rc6. For detailed information about the fix and affected versions, refer to the Red Hat Bug Report #2041547. Organizations should update to the latest stable kernel version provided by their distribution vendor.

Workarounds

• Disable unprivileged eBPF to prevent non-root users from loading eBPF programs
• Restrict access to systems where eBPF functionality is required only to trusted administrators
• Implement mandatory access control (SELinux/AppArmor) policies to limit eBPF usage
• Consider containerization with restricted capabilities to limit exposure

# Configuration example - Disable unprivileged eBPF access
# Add to /etc/sysctl.conf or /etc/sysctl.d/99-security.conf
echo "kernel.unprivileged_bpf_disabled=1" >> /etc/sysctl.d/99-bpf-security.conf

# Apply immediately without reboot
sysctl -p /etc/sysctl.d/99-bpf-security.conf

# Verify the setting is applied
sysctl kernel.unprivileged_bpf_disabled