CVE-2023-52440
📋 TL;DR
A buffer overflow vulnerability in the Linux kernel's ksmbd component allows attackers to overflow session key buffers during NTLMSSP authentication. This affects systems using the ksmbd SMB server module in the Linux kernel. Attackers could potentially execute arbitrary code or cause denial of service.
💻 Affected Systems
- Linux kernel with ksmbd module
📦 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 →⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to full system compromise, privilege escalation to kernel level, or persistent backdoor installation.
Likely Case
Kernel panic or system crash causing denial of service, potentially leading to data corruption or system instability.
If Mitigated
Limited impact if proper network segmentation, access controls, and exploit mitigations are in place.
🎯 Exploit Status
Requires ability to send crafted NTLMSSP authentication blobs to ksmbd server. Authentication attempt needed but not necessarily successful authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Patched in Linux kernel stable releases via commits referenced in CVE
Vendor Advisory: https://git.kernel.org/stable/c/30fd6521b2fbd9b767e438e31945e5ea3e3a2fba
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution's repositories. 2. Reboot system to load new kernel. 3. Verify ksmbd module is updated.
🔧 Temporary Workarounds
Disable ksmbd module
linuxUnload ksmbd kernel module if not required
sudo rmmod ksmbd
echo 'blacklist ksmbd' | sudo tee /etc/modprobe.d/ksmbd-blacklist.conf
Restrict SMB access
linuxUse firewall rules to limit access to ksmbd server
sudo iptables -A INPUT -p tcp --dport 445 -s trusted_network -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 445 -j DROP
🧯 If You Can't Patch
- Disable ksmbd module entirely if SMB server functionality is not required
- Implement strict network segmentation and firewall rules to limit access to ksmbd servers
🔍 How to Verify
Check if Vulnerable:
Check if ksmbd module is loaded: lsmod | grep ksmbd. If loaded, check kernel version against patched releases.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits: uname -r and check with distribution vendor. Confirm ksmbd module version if possible.📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- ksmbd authentication failures with unusual SessionKey lengths
- system crashes during SMB authentication
Network Indicators:
- Unusual NTLMSSP authentication attempts to port 445
- Multiple failed authentication attempts with varying blob sizes
SIEM Query:
source="kernel" AND ("panic" OR "Oops") OR source="ksmbd" AND "auth" AND "SessionKey"🔗 References
- https://git.kernel.org/stable/c/30fd6521b2fbd9b767e438e31945e5ea3e3a2fba
- https://git.kernel.org/stable/c/4b081ce0d830b684fdf967abc3696d1261387254
- https://git.kernel.org/stable/c/7f1d6cb0eb6af3a8088dc24b7ddee9a9711538c4
- https://git.kernel.org/stable/c/bd554ed4fdc3d38404a1c43d428432577573e809
- https://git.kernel.org/stable/c/ecd7e1c562cb08e41957fcd4b0e404de5ab38e20
- https://git.kernel.org/stable/c/30fd6521b2fbd9b767e438e31945e5ea3e3a2fba
- https://git.kernel.org/stable/c/4b081ce0d830b684fdf967abc3696d1261387254
- https://git.kernel.org/stable/c/7f1d6cb0eb6af3a8088dc24b7ddee9a9711538c4
- https://git.kernel.org/stable/c/bd554ed4fdc3d38404a1c43d428432577573e809
- https://git.kernel.org/stable/c/ecd7e1c562cb08e41957fcd4b0e404de5ab38e20
