CVE-2025-21936
📋 TL;DR
This CVE describes a null pointer dereference vulnerability in the Linux kernel's Bluetooth subsystem. When mgmt_alloc_skb() fails to allocate memory in mgmt_device_connected(), the kernel could crash, causing denial of service. This affects Linux systems with Bluetooth enabled.
💻 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 requiring physical or remote reboot.
Likely Case
System instability or crash when Bluetooth device connections fail under memory pressure.
If Mitigated
Minor performance impact from additional error checking with no security breach.
🎯 Exploit Status
Exploitation requires triggering specific Bluetooth connection scenarios under memory constraints.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Multiple stable kernel versions with commits: 7841180342c9a0fd97d54f3e62c7369309b5cd84, 7d39387886ffe220323cbed5c155233c3276926b, bdb1805c248e9694dbb3ffa8867cef2e52cf7261, d8df010f72b8a32aaea393e36121738bb53ed905, dc516e66fb28c61b248b393e2ddd63bd7f104969
Vendor Advisory: https://git.kernel.org/stable/c/
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version. 2. Reboot system. 3. Verify kernel version matches patched release.
🔧 Temporary Workarounds
Disable Bluetooth
linuxDisable Bluetooth functionality to prevent exploitation
sudo systemctl stop bluetooth
sudo systemctl disable bluetooth
sudo rfkill block bluetooth
🧯 If You Can't Patch
- Disable Bluetooth functionality entirely
- Implement strict memory limits and monitoring to prevent allocation failures
🔍 How to Verify
Check if Vulnerable:
Check kernel version and compare with patched versions in git commits. Use 'uname -r' and examine Bluetooth subsystem logs for allocation failures.Check Version:
uname -rVerify Fix Applied:
Verify kernel version is updated to patched version and test Bluetooth connectivity under memory pressure.📡 Detection & Monitoring
Log Indicators:
- Kernel panic logs
- Bluetooth subsystem error messages
- Memory allocation failure logs
Network Indicators:
- Unusual Bluetooth connection attempts followed by system instability
SIEM Query:
source="kernel" AND ("panic" OR "Oops" OR "null pointer dereference") AND "bluetooth"🔗 References
- https://git.kernel.org/stable/c/7841180342c9a0fd97d54f3e62c7369309b5cd84
- https://git.kernel.org/stable/c/7d39387886ffe220323cbed5c155233c3276926b
- https://git.kernel.org/stable/c/bdb1805c248e9694dbb3ffa8867cef2e52cf7261
- https://git.kernel.org/stable/c/d8df010f72b8a32aaea393e36121738bb53ed905
- https://git.kernel.org/stable/c/dc516e66fb28c61b248b393e2ddd63bd7f104969
- https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html
