CVE-2023-38432
📋 TL;DR
This vulnerability in the Linux kernel's ksmbd SMB server allows attackers to trigger an out-of-bounds read by sending specially crafted SMB packets with mismatched payload size and RFC1002 length specifications. Systems running Linux kernels before 6.3.10 with ksmbd enabled are affected, potentially leading to information disclosure or system crashes.
💻 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 by Netapp
⚠️ Risk & Real-World Impact
Worst Case
Information disclosure of kernel memory contents, potential kernel panic leading to denial of service, or as a stepping stone for further exploitation.
Likely Case
Denial of service through kernel panic or system crash, with possible information leakage from kernel memory.
If Mitigated
Limited impact if ksmbd is disabled or network access is restricted; patched systems are unaffected.
🎯 Exploit Status
Exploitation requires sending specially crafted SMB packets to the vulnerable service. No authentication needed if service is accessible.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel 6.3.10 and later
Vendor Advisory: https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.3.10
Restart Required: Yes
Instructions:
1. Update Linux kernel to version 6.3.10 or later. 2. For distributions: Use package manager (apt/yum/dnf) to update kernel package. 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 network access
linuxUse firewall rules to block access to SMB ports
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
- Implement strict network segmentation and firewall rules to limit SMB access
🔍 How to Verify
Check if Vulnerable:
Check if ksmbd module is loaded: lsmod | grep ksmbd. Check kernel version: uname -rCheck Version:
uname -rVerify Fix Applied:
Verify kernel version is 6.3.10 or later: uname -r. Confirm ksmbd is not loaded or updated.📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- ksmbd service crashes
- unusual SMB protocol errors
Network Indicators:
- Malformed SMB packets with size/length mismatches
- unusual traffic to port 445/139
SIEM Query:
source="kernel" AND ("panic" OR "Oops") OR source="ksmbd" AND ("error" OR "crash")🔗 References
- https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.3.10
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/smb/server?id=2b9b8f3b68edb3d67d79962f02e26dbb5ae3808d
- https://security.netapp.com/advisory/ntap-20230831-0002/
- https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.3.10
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/smb/server?id=2b9b8f3b68edb3d67d79962f02e26dbb5ae3808d
- https://security.netapp.com/advisory/ntap-20230831-0002/
