CVE-2023-32247
📋 TL;DR
This vulnerability in the Linux kernel's ksmbd SMB server allows attackers to cause denial-of-service by exploiting improper resource consumption handling during SMB2 session setup. Systems running affected Linux kernel versions with ksmbd enabled are vulnerable. The flaw requires network access to the SMB service.
💻 Affected Systems
- Linux kernel ksmbd module
📦 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 →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
Complete system unavailability due to resource exhaustion, potentially requiring reboot to restore service.
Likely Case
SMB service disruption affecting file sharing and authentication services, with possible kernel instability.
If Mitigated
Minimal impact if ksmbd is disabled or properly firewalled, with only authenticated users affected.
🎯 Exploit Status
Exploitation requires sending crafted SMB2_SESSION_SETUP packets to the ksmbd service.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel versions with commit addressing CVE-2023-32247
Vendor Advisory: https://access.redhat.com/security/cve/CVE-2023-32247
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution. 2. Reboot system. 3. Verify ksmbd module loads patched version.
🔧 Temporary Workarounds
Disable ksmbd module
linuxPrevent loading of vulnerable ksmbd kernel module
echo 'blacklist ksmbd' >> /etc/modprobe.d/blacklist-ksmbd.conf
rmmod ksmbd
Firewall SMB ports
linuxBlock access to SMB ports (445/tcp, 139/tcp)
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 completely if not required
- Implement network segmentation to restrict SMB access to trusted hosts only
🔍 How to Verify
Check if Vulnerable:
Check if ksmbd module is loaded: lsmod | grep ksmbdCheck Version:
uname -rVerify Fix Applied:
Check kernel version is patched: uname -r and verify against distribution security advisories📡 Detection & Monitoring
Log Indicators:
- Kernel logs showing ksmbd resource exhaustion
- Multiple failed SMB2_SESSION_SETUP attempts
Network Indicators:
- Unusual volume of SMB2_SESSION_SETUP packets
- Traffic to port 445 from unexpected sources
SIEM Query:
source="kernel" AND "ksmbd" AND ("resource" OR "exhaustion" OR "denial")🔗 References
- https://access.redhat.com/security/cve/CVE-2023-32247
- https://bugzilla.redhat.com/show_bug.cgi?id=2219803
- https://security.netapp.com/advisory/ntap-20230915-0011/
- https://www.zerodayinitiative.com/advisories/ZDI-CAN-20478/
- https://access.redhat.com/security/cve/CVE-2023-32247
- https://bugzilla.redhat.com/show_bug.cgi?id=2219803
- https://security.netapp.com/advisory/ntap-20230915-0011/
- https://www.zerodayinitiative.com/advisories/ZDI-CAN-20478/
