CVE-2023-53338
📋 TL;DR
This CVE describes a use-after-free vulnerability in the Linux kernel's BPF (Berkeley Packet Filter) xmit operations. When BPF programs return certain positive values from redirect operations, the kernel incorrectly treats them as continuation signals, allowing freed memory buffers to be processed further, potentially causing kernel crashes or arbitrary code execution. This affects systems running vulnerable Linux kernel versions with BPF/LWT (Light Weight Tunnel) functionality enabled.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash, potential privilege escalation to kernel mode, or arbitrary code execution with kernel privileges.
Likely Case
System instability, kernel crashes, denial of service conditions, or memory corruption leading to unpredictable behavior.
If Mitigated
Limited impact if BPF/LWT functionality is disabled or restricted to trusted users only.
🎯 Exploit Status
Exploitation requires ability to load BPF programs (typically root or CAP_BPF privileges). The vulnerability is in error handling code, making reliable exploitation challenging but possible with skilled attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing the fix commits: 065d5f17096ec9161180e2c890afdff4dc6125f2, 29b22badb7a84b783e3a4fffca16f7768fb31205, 65583f9e070db7bece20710cfa2e3daeb0b831d9, 67f8f2bae8e7ac72e09def2b667e44704c4d1ee1, a97f221651fcdc891166e9bc270e3d9bfa5a0080
Vendor Advisory: https://git.kernel.org/stable/c/
Restart Required: Yes
Instructions:
1. Update Linux kernel to a version containing the fix commits. 2. For distributions: Use package manager (apt/yum/dnf) to install latest kernel updates. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable BPF JIT and restrict BPF
linuxRestrict BPF program loading to prevent exploitation
sysctl -w kernel.unprivileged_bpf_disabled=1
sysctl -w net.core.bpf_jit_enable=0
Remove CAP_BPF from non-root users
linuxPrevent non-root users from loading BPF programs
setcap -r CAP_BPF /path/to/programs
Review capabilities with: getcap -r /
🧯 If You Can't Patch
- Restrict BPF program loading to trusted users only using Linux capabilities (remove CAP_BPF from unnecessary users/processes)
- Implement strict monitoring for kernel crashes or unusual BPF program behavior using system logs and monitoring tools
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if BPF/LWT is enabled: uname -r and check if BPF syscalls are being usedCheck Version:
uname -rVerify Fix Applied:
Verify kernel version is updated to one containing the fix commits: uname -r and check with distribution's security advisories📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages in /var/log/kern.log or dmesg
- OOM killer activity related to network operations
- BPF program loading errors
Network Indicators:
- Unusual network traffic patterns from BPF programs
- Increased kernel memory usage during network operations
SIEM Query:
source="kernel" AND ("panic" OR "use-after-free" OR "BPF" OR "LWT")🔗 References
- https://git.kernel.org/stable/c/065d5f17096ec9161180e2c890afdff4dc6125f2
- https://git.kernel.org/stable/c/29b22badb7a84b783e3a4fffca16f7768fb31205
- https://git.kernel.org/stable/c/65583f9e070db7bece20710cfa2e3daeb0b831d9
- https://git.kernel.org/stable/c/67f8f2bae8e7ac72e09def2b667e44704c4d1ee1
- https://git.kernel.org/stable/c/a97f221651fcdc891166e9bc270e3d9bfa5a0080
- https://git.kernel.org/stable/c/d68c17402442f5f494a2c3ebde5cb82f6aa9160a
- https://git.kernel.org/stable/c/e3f647e4b642f9f6d32795a16f92c116c138d2af
