CVE-2025-39684
📋 TL;DR
This CVE describes an information leak vulnerability in the Linux kernel's comedi subsystem, where uninitialized kernel memory can be exposed to userspace. Attackers with local access can potentially read sensitive kernel data. Systems using comedi drivers for data acquisition hardware are primarily affected.
💻 Affected Systems
- Linux kernel with comedi subsystem enabled
📦 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel memory disclosure could reveal sensitive information like encryption keys, passwords, or other process data, potentially enabling further privilege escalation attacks.
Likely Case
Information leak exposing kernel memory contents, which could aid attackers in bypassing security mechanisms or preparing more sophisticated attacks.
If Mitigated
Minimal impact with proper access controls limiting local user privileges and kernel hardening measures in place.
🎯 Exploit Status
Requires local access and knowledge of comedi subsystem usage. Exploitation depends on specific hardware drivers being loaded.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits 3cd212e895ca2d58963fdc6422502b10dd3966bb, 868a1b68dcd9f2805bb86aa64862402f785d8c4a, aecf0d557ddd95ce68193a5ee1dc4c87415ff08a, d84f6e77ebe3359394df32ecd97e0d76a25283dc, or f3b0c9ec54736f3b8118f93a473d22e11ee65743
Vendor Advisory: https://git.kernel.org/stable/c/3cd212e895ca2d58963fdc6422502b10dd3966bb
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution's repositories. 2. Reboot system to load new kernel. 3. Verify comedi module is not loaded if not needed.
🔧 Temporary Workarounds
Disable comedi module
LinuxPrevent loading of vulnerable comedi subsystem if not required
echo 'blacklist comedi' >> /etc/modprobe.d/blacklist-comedi.conf
rmmod comedi
🧯 If You Can't Patch
- Restrict local user access to systems with comedi hardware
- Implement strict privilege separation and limit users who can access comedi devices
🔍 How to Verify
Check if Vulnerable:
Check if comedi module is loaded: lsmod | grep comedi. If loaded, check kernel version against patched versions.Check Version:
uname -rVerify Fix Applied:
Verify kernel version includes fix commits and comedi module version is updated. Test with comedi hardware if available.📡 Detection & Monitoring
Log Indicators:
- Unusual comedi device access by non-privileged users
- Kernel oops or warnings related to comedi
Network Indicators:
- None - local vulnerability only
SIEM Query:
process.name: "comedi" AND user.privileges: "low"🔗 References
- https://git.kernel.org/stable/c/3cd212e895ca2d58963fdc6422502b10dd3966bb
- https://git.kernel.org/stable/c/868a1b68dcd9f2805bb86aa64862402f785d8c4a
- https://git.kernel.org/stable/c/aecf0d557ddd95ce68193a5ee1dc4c87415ff08a
- https://git.kernel.org/stable/c/d84f6e77ebe3359394df32ecd97e0d76a25283dc
- https://git.kernel.org/stable/c/f3b0c9ec54736f3b8118f93a473d22e11ee65743
- https://git.kernel.org/stable/c/ff4a7c18799c7fe999fa56c5cf276e13866b8c1a
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
