CVE-2023-52751
📋 TL;DR
This is a use-after-free vulnerability in the Linux kernel's SMB client implementation (cifs.ko). It allows attackers with access to a malicious SMB server to potentially execute arbitrary code or cause denial of service on vulnerable Linux systems. Systems using SMB/CIFS mounts with specific configurations 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 →⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with kernel privileges leading to complete system compromise.
Likely Case
Kernel panic or system crash causing denial of service.
If Mitigated
Limited impact if proper network segmentation and SMB server trust controls are in place.
🎯 Exploit Status
Requires control of SMB server or ability to intercept/modify SMB traffic. Race condition makes exploitation timing-sensitive.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in kernel stable commits: 5c86919455c1edec99ebd3338ad213b59271a71b, 6db94d08359c43f2c8fe372811cdee04564a41b9, 93877b9afc2994c89362007aac480a7b150f386f
Vendor Advisory: https://git.kernel.org/stable/c/5c86919455c1edec99ebd3338ad213b59271a71b
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fix. 2. Check your distribution's security advisories. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Disable vulnerable SMB mount options
linuxAvoid using the specific mount options that trigger the vulnerability
# Review /etc/fstab and mount commands for: multichannel,max_channels=2,vers=3.1.1,mfsymlinks,noperm
# Remove or modify these options
Restrict SMB server access
allOnly mount SMB shares from trusted servers
# Implement firewall rules to restrict SMB access
# Use network segmentation for SMB traffic
🧯 If You Can't Patch
- Implement strict network segmentation to isolate SMB traffic
- Monitor for kernel panic/crash events related to cifs module
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if cifs module is loaded with vulnerable options: uname -r; lsmod | grep cifs; mount | grep cifsCheck Version:
uname -rVerify Fix Applied:
Verify kernel version is patched and test SMB mounts with previously problematic options📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- KASAN reports of use-after-free in smb2_query_info_compound
- CIFS lease break errors in system logs
Network Indicators:
- Unusual SMB traffic patterns to/from Linux clients
- Multiple SMB compound requests
SIEM Query:
source="kernel" AND ("KASAN" OR "use-after-free" OR "smb2_query_info_compound" OR "CIFS: VFS: No task to wake")🔗 References
- https://git.kernel.org/stable/c/5c86919455c1edec99ebd3338ad213b59271a71b
- https://git.kernel.org/stable/c/6db94d08359c43f2c8fe372811cdee04564a41b9
- https://git.kernel.org/stable/c/93877b9afc2994c89362007aac480a7b150f386f
- https://git.kernel.org/stable/c/5c86919455c1edec99ebd3338ad213b59271a71b
- https://git.kernel.org/stable/c/6db94d08359c43f2c8fe372811cdee04564a41b9
- https://git.kernel.org/stable/c/93877b9afc2994c89362007aac480a7b150f386f
