CVE-2023-4458
📋 TL;DR
CVE-2023-4458 is an out-of-bounds read vulnerability in the Linux kernel's ksmbd module when parsing extended attributes. This allows attackers to read sensitive kernel memory and potentially leak information. Only systems with the ksmbd SMB server module enabled are affected.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel memory disclosure leading to information leakage that could aid further attacks, including potential privilege escalation if combined with other vulnerabilities.
Likely Case
Limited information disclosure from kernel memory, potentially exposing system information or sensitive data structures.
If Mitigated
No impact if ksmbd is disabled or patched, as the vulnerability requires the module to be active and accessible.
🎯 Exploit Status
Requires access to ksmbd service; exploitation details not publicly documented.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Linux kernel 6.5.7, 6.1.49, 5.15.128 and later
Vendor Advisory: https://access.redhat.com/security/cve/CVE-2023-4458
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version via distribution package manager. 2. Reboot system to load new kernel. 3. Verify ksmbd module loads from patched kernel.
🔧 Temporary Workarounds
Disable ksmbd module
linuxPrevent loading of vulnerable ksmbd kernel module
sudo modprobe -r ksmbd
echo 'blacklist ksmbd' | sudo tee /etc/modprobe.d/ksmbd-blacklist.conf
Block ksmbd network access
linuxBlock SMB ports used by ksmbd
sudo iptables -A INPUT -p tcp --dport 445 -j DROP
sudo iptables -A INPUT -p tcp --dport 139 -j DROP
🧯 If You Can't Patch
- Disable ksmbd module if not required for business operations
- Implement network segmentation to restrict access to ksmbd services
🔍 How to Verify
Check if Vulnerable:
Check if ksmbd module is loaded: lsmod | grep ksmbdCheck Version:
uname -rVerify Fix Applied:
Check kernel version: uname -r and verify it's patched version; verify ksmbd module loads from new kernel📡 Detection & Monitoring
Log Indicators:
- Kernel oops messages related to ksmbd
- Unexpected ksmbd process crashes
Network Indicators:
- Unusual SMB traffic patterns to ksmbd ports
SIEM Query:
process.name:"ksmbd" AND (event.action:"crash" OR log.level:"error")