CVE-2023-53221
📋 TL;DR
This CVE describes a memory leak vulnerability in the Linux kernel's BPF subsystem where failed fentry attachments leave allocated trampoline images in memory. This affects systems running vulnerable Linux kernel versions with BPF enabled. The vulnerability allows attackers to cause resource exhaustion over time.
💻 Affected Systems
- Linux kernel
📦 What is this software?
Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →Linux Kernel by Linux
The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...
Learn more about Linux Kernel →⚠️ Risk & Real-World Impact
Worst Case
Sustained exploitation could lead to kernel memory exhaustion, causing system instability, denial of service, or potential kernel crashes.
Likely Case
Gradual memory consumption leading to performance degradation over time, potentially requiring system reboots to clear accumulated memory.
If Mitigated
Minimal impact with proper monitoring and memory limits in place, though some performance overhead may still occur.
🎯 Exploit Status
Exploitation requires ability to load BPF programs and trigger fentry attachment failures. The provided example shows a specific case with trap_init function.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Patches available in stable kernel trees (see references for specific commits)
Vendor Advisory: https://git.kernel.org/stable/c/108598c39eefbedc9882273ac0df96127a629220
Restart Required: Yes
Instructions:
1. Update to a patched kernel version from your distribution's repositories. 2. Reboot the system to load the new kernel. 3. Verify the fix by checking kernel version and testing BPF fentry attachments.
🔧 Temporary Workarounds
Restrict BPF program loading
linuxLimit which users can load BPF programs to reduce attack surface
sysctl -w kernel.unprivileged_bpf_disabled=1
capsh --drop=cap_bpf,cap_sys_admin -- -c 'your_command'
🧯 If You Can't Patch
- Implement strict monitoring of kernel memory usage and BPF program loading
- Restrict BPF capabilities to only essential users and applications
🔍 How to Verify
Check if Vulnerable:
Check for leftover trampoline images: tail /proc/kallsyms | grep bpf_trampolineCheck Version:
uname -rVerify Fix Applied:
After patching, attempt to reproduce the failing fentry attachment and verify no leftover trampoline images remain📡 Detection & Monitoring
Log Indicators:
- Kernel logs showing BPF program loading failures
- System logs showing abnormal memory consumption patterns
Network Indicators:
- Not applicable - local vulnerability
SIEM Query:
source="kernel" AND ("bpf" OR "trampoline") AND ("failed" OR "error")