CVE-2023-53685
📋 TL;DR
A memory leak vulnerability in the Linux kernel's TUN/TAP driver occurs when a network queue is detached while NAPI (New API) and multi-queue features are enabled. This allows unprivileged local users to cause kernel memory exhaustion by repeatedly triggering the condition. Systems using TUN/TAP interfaces with NAPI and multi-queue enabled are affected.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Local attackers can cause kernel memory exhaustion leading to system instability, denial of service, or potential kernel crashes.
Likely Case
Local users can degrade system performance through memory exhaustion, potentially affecting other processes and network functionality.
If Mitigated
With proper access controls, only authorized users can trigger the vulnerability, limiting impact to controlled environments.
🎯 Exploit Status
The vulnerability report includes a reproduction code snippet. Exploitation requires local access and ability to create/manipulate TUN/TAP devices.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits 0d20210a190f76db9ec35ee4e0fc77e6c7a148f5, 82b2bc279467c875ec36f8ef820f00997c2a4e8e, or 9cae243b9ae25adfe468cd47ceca591f6725b79c
Vendor Advisory: https://git.kernel.org/stable/c/0d20210a190f76db9ec35ee4e0fc77e6c7a148f5
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution vendor. 2. Reboot system to load new kernel. 3. Verify kernel version matches patched release.
🔧 Temporary Workarounds
Disable TUN/TAP device creation
LinuxPrevent unprivileged users from creating TUN/TAP devices
echo 'install tun /bin/false' >> /etc/modprobe.d/disable-tun.conf
rmmod tun
Restrict TUN/TAP device permissions
LinuxLimit access to /dev/net/tun to privileged users only
chmod 600 /dev/net/tun
chown root:root /dev/net/tun
🧯 If You Can't Patch
- Implement strict access controls on /dev/net/tun device
- Monitor system memory usage for unusual patterns indicating potential exploitation
🔍 How to Verify
Check if Vulnerable:
Check if kernel version is before the fix commits. For example: uname -r and compare with distribution's patched versions.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits. Check with: grep -q 'tun.*detached.*NAPI' /proc/kallsyms (not reliable on all systems) or verify kernel source has the patch.📡 Detection & Monitoring
Log Indicators:
- Kernel oops messages related to memory allocation failures
- System logs showing repeated TUN/TAP device creation/destruction
- dmesg output showing 'unreferenced object' memory leak warnings
Network Indicators:
- Unusual TUN/TAP interface creation patterns
- Increased kernel memory usage without corresponding user process growth
SIEM Query:
source="kernel" AND ("tun" OR "TUNSETQUEUE" OR "IFF_DETACH_QUEUE") AND ("memory" OR "leak" OR "oom")