CVE-2025-38717
📋 TL;DR
A race condition vulnerability exists in the Linux kernel's KCM (Kernel Connection Multiplexor) subsystem where simultaneous execution of kcm_unattach() and kcm_release() functions can cause a use-after-free condition. This affects Linux systems using KCM for socket multiplexing, potentially leading to kernel crashes or privilege escalation. The vulnerability requires local access to exploit.
💻 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 →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
Local privilege escalation to root, kernel panic causing system crash, or arbitrary code execution in kernel context.
Likely Case
Kernel panic leading to denial of service (system crash) or system instability.
If Mitigated
No impact if KCM is not used or proper kernel hardening is in place.
🎯 Exploit Status
Race condition exploitation requires precise timing and local access. Discovered by syzbot fuzzing.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions with commits 52565a935213cd6a8662ddb8efe5b4219343a25d, 7275dc3bb8f91b23125ff3f47b6529935cf46152, 798733ee5d5788b12e8a52db1519abc17e826f69, or c0bffbc92a1ca3960fb9cdb8e9f75a68468eb308
Vendor Advisory: https://git.kernel.org/stable/c/52565a935213cd6a8662ddb8efe5b4219343a25d
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution vendor. 2. Reboot system to load new kernel. 3. Verify KCM module is not loaded if not needed.
🔧 Temporary Workarounds
Disable KCM module
LinuxPrevent loading of KCM kernel module if not required
echo 'install kcm /bin/false' >> /etc/modprobe.d/disable-kcm.conf
rmmod kcm 2>/dev/null || true
🧯 If You Can't Patch
- Disable KCM module via modprobe blacklist
- Restrict local user access to systems where KCM is required
🔍 How to Verify
Check if Vulnerable:
Check if KCM module is loaded: lsmod | grep kcm. If loaded, check kernel version against patched versions.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes fix commits and KCM module version. Check dmesg for any KCM-related crashes.📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages in /var/log/messages or journalctl
- Kernel oops messages related to kcm or net/kcm
Network Indicators:
- None - local exploitation only
SIEM Query:
source="kernel" AND ("kcm" OR "KCM" OR "kernel panic")