CVE-2023-38426
📋 TL;DR
This vulnerability in the Linux kernel's ksmbd SMB server allows attackers to read memory beyond allocated buffers when processing SMB2 create context requests. It affects Linux systems running kernel versions before 6.3.4 with ksmbd enabled. Attackers could potentially leak sensitive kernel memory or cause system instability.
💻 Affected Systems
- Linux kernel
📦 What is this software?
H300s by Netapp
H410s by Netapp
H500s by Netapp
H700s by Netapp
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 →Solidfire \& Hci Management Node by Netapp
⚠️ Risk & Real-World Impact
Worst Case
Kernel memory disclosure leading to information leakage, potential privilege escalation, or denial of service through kernel panic.
Likely Case
Information disclosure of kernel memory contents, potentially exposing sensitive data or system information.
If Mitigated
Minimal impact if ksmbd is disabled or proper network segmentation prevents access.
🎯 Exploit Status
Exploitation requires sending specially crafted SMB2 packets to ksmbd service. Authentication status depends on SMB share configuration.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel 6.3.4 and later
Vendor Advisory: https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.3.4
Restart Required: Yes
Instructions:
1. Update Linux kernel to version 6.3.4 or later. 2. For distributions with backported patches, apply security updates. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable ksmbd module
linuxPrevent loading of vulnerable ksmbd kernel module
echo 'blacklist ksmbd' >> /etc/modprobe.d/blacklist-ksmbd.conf
rmmod ksmbd
Block SMB ports at firewall
linuxPrevent external access to ksmbd service
iptables -A INPUT -p tcp --dport 445 -j DROP
iptables -A INPUT -p tcp --dport 139 -j DROP
🧯 If You Can't Patch
- Disable ksmbd service if not required for business operations
- Implement strict network segmentation to isolate systems with ksmbd enabled
🔍 How to Verify
Check if Vulnerable:
Check kernel version: uname -r and verify if ksmbd module is loaded: lsmod | grep ksmbdCheck Version:
uname -rVerify Fix Applied:
Verify kernel version is 6.3.4 or later: uname -r and check that ksmbd module is either not loaded or patched version📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- ksmbd error messages in system logs
- unusual SMB connection attempts
Network Indicators:
- Unusual SMB2 create context requests with malformed name_len values
- Traffic to port 445/139 with abnormal packet patterns
SIEM Query:
source="kernel" AND ("panic" OR "Oops") OR source="ksmbd" AND ("error" OR "out of bounds")🔗 References
- https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.3.4
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/ksmbd?id=02f76c401d17e409ed45bf7887148fcc22c93c85
- https://security.netapp.com/advisory/ntap-20230915-0010/
- https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.3.4
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/ksmbd?id=02f76c401d17e409ed45bf7887148fcc22c93c85
- https://security.netapp.com/advisory/ntap-20230915-0010/
