CVE-2025-21670
📋 TL;DR
A NULL pointer dereference vulnerability in the Linux kernel's vsock/bpf subsystem allows local attackers to cause a kernel panic (denial of service) by triggering a failed vsock connection and then attempting to receive data. This affects systems with vsock sockets and BPF enabled, primarily Linux servers and containers.
💻 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 →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 →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 leading to system crash and denial of service, potentially disrupting critical services.
Likely Case
Local denial of service through kernel crash, requiring system reboot to recover.
If Mitigated
Minimal impact with proper access controls limiting local user privileges.
🎯 Exploit Status
Exploitation requires local access and ability to create vsock sockets. No privilege escalation demonstrated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Patched in kernel stable releases via commits: 58e586c30d0b6f5dc0174a41026f2b0a48c9aab6, 6771e1279dadf1d92a72e1465134257d9e6f2459, f6abafcd32f9cfc4b1a2f820ecea70773e26d423
Vendor Advisory: https://git.kernel.org/stable/c/58e586c30d0b6f5dc0174a41026f2b0a48c9aab6
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution. 2. Reboot system to load new kernel. 3. Verify kernel version matches patched release.
🔧 Temporary Workarounds
Disable vsock module
linuxPrevent loading of vsock kernel module if not required
echo 'install vsock /bin/false' >> /etc/modprobe.d/disable-vsock.conf
rmmod vsock 2>/dev/null || true
Restrict BPF system calls
linuxLimit BPF functionality using seccomp or kernel parameters
sysctl -w kernel.unprivileged_bpf_disabled=1
🧯 If You Can't Patch
- Implement strict access controls to limit local user privileges
- Use container security policies to restrict vsock and BPF capabilities
🔍 How to Verify
Check if Vulnerable:
Check kernel version and compare with patched releases from your distribution. Test by attempting to reproduce crash with vsock program.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes the fix commits. Test vsock functionality to ensure no crashes occur.📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages in /var/log/kern.log or dmesg
- NULL pointer dereference errors with vsock_bpf_recvmsg in stack traces
Network Indicators:
- Unusual vsock connection attempts from local processes
SIEM Query:
source="kernel" AND "NULL pointer dereference" AND "vsock"