CVE-2024-56721
📋 TL;DR
A missing termination entry in the erratum_1386_microcode array in the Linux kernel's x86/CPU/AMD subsystem could cause the x86_match_cpu_with_stepping() function to read beyond the array bounds. This affects Linux systems running on AMD processors with specific microcode versions. The vulnerability could lead to kernel instability or potential information disclosure.
💻 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
Kernel panic, system crash, or potential information disclosure from kernel memory if an attacker can trigger the out-of-bounds read repeatedly.
Likely Case
System instability, crashes, or unpredictable behavior when the kernel attempts to match CPU stepping with microcode patches.
If Mitigated
Minimal impact if systems are not using affected AMD processors or have updated microcode/kernel.
🎯 Exploit Status
Exploitation requires local access and ability to trigger the CPU stepping matching function. No public exploits are known at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions with commits 82d6b82cf89d950982ac240ba068c3a7e1f23b0a, ccfee14f08b8699132b87bc6d78e0fa75bf094dd, or ff6cdc407f4179748f4673c39b0921503199a0ad
Vendor Advisory: https://git.kernel.org/stable/c/82d6b82cf89d950982ac240ba068c3a7e1f23b0a
Restart Required: Yes
Instructions:
1. Update to a patched kernel version from your distribution's repositories. 2. Apply AMD microcode updates if available. 3. Reboot the system to load the new kernel.
🔧 Temporary Workarounds
Disable affected CPU features
linuxPotentially disable microcode updates or specific CPU features if not required, though this may impact performance or security.
🧯 If You Can't Patch
- Restrict local access to affected systems to trusted users only
- Implement strict monitoring for kernel crashes or unusual system behavior
🔍 How to Verify
Check if Vulnerable:
Check kernel version and whether it contains the vulnerable code. Use 'uname -r' and compare with affected versions.Check Version:
uname -rVerify Fix Applied:
Verify kernel version is updated to a version containing the fix commits. Check dmesg for microcode update messages.📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- Microcode update failures
- System crashes in dmesg
SIEM Query:
source="kernel" AND ("panic" OR "Oops" OR "microcode" AND "error")