CVE-2022-50372
📋 TL;DR
This CVE describes a memory leak vulnerability in the Linux kernel's CIFS/SMB client when building NTLMSSP authentication blobs fails during SMB session setup. It affects systems mounting CIFS/SMB shares, potentially leading to resource exhaustion. The vulnerability requires local access to trigger.
💻 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
An attacker with local access could repeatedly trigger failed NTLMSSP negotiations to exhaust kernel memory, causing system instability or denial of service.
Likely Case
Accidental triggering during CIFS mount failures could cause minor memory leaks, but unlikely to be weaponized for significant impact.
If Mitigated
With proper access controls, the impact is minimal as it requires local user privileges and specific CIFS mount operations.
🎯 Exploit Status
Exploitation requires local access and ability to mount CIFS shares with specific authentication failures.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel with commit 30b2d7f8f13664655480d6af45f60270b3eb6736 or later
Vendor Advisory: https://git.kernel.org/stable/c/30b2d7f8f13664655480d6af45f60270b3eb6736
Restart Required: No
Instructions:
1. Update Linux kernel to version containing the fix commit
2. For distributions: Apply kernel security updates from your vendor
3. Reboot is recommended but not strictly required for kernel updates
🔧 Temporary Workarounds
Disable CIFS/SMB mounting
allPrevent use of CIFS/SMB client functionality to avoid triggering the vulnerability
# Blacklist cifs module: echo 'blacklist cifs' >> /etc/modprobe.d/blacklist.conf
# Unload module if loaded: rmmod cifs
🧯 If You Can't Patch
- Restrict local user access to prevent unauthorized CIFS mount attempts
- Monitor system memory usage and kernel logs for signs of memory exhaustion
🔍 How to Verify
Check if Vulnerable:
Check kernel version and verify if CIFS module is loaded: lsmod | grep cifs && uname -rCheck Version:
uname -rVerify Fix Applied:
Verify kernel version includes fix commit: git log --oneline | grep -i '30b2d7f8f13664655480d6af45f60270b3eb6736'📡 Detection & Monitoring
Log Indicators:
- Kernel logs showing 'mount.cifs' failures
- Memory allocation failures in kernel logs
- OOM killer events related to CIFS operations
Network Indicators:
- Failed SMB authentication attempts from local systems
SIEM Query:
source="kernel" AND ("mount.cifs" OR "cifs" OR "SMB2_sess") AND ("failed" OR "error" OR "leak")