CVE-2025-21925
📋 TL;DR
A Linux kernel vulnerability in the LLC (Logical Link Control) subsystem allows a local attacker to cause a kernel panic (denial of service) by triggering a BUG_ON condition when transmitting packets through network devices that don't support IFF_TX_SKB_SHARING. This affects Linux systems using the LLC protocol stack.
💻 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 →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 complete denial of service, requiring physical or remote console access to reboot.
Likely Case
Local denial of service through kernel panic, disrupting all services on the affected system.
If Mitigated
No impact if patched or if LLC protocol is not used.
🎯 Exploit Status
Syzbot found and reported the crash. Exploitation requires local access to send LLC packets.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions with commits 056e8a46d79e22983bae4267e0d9c52927076f46 or backported fixes
Vendor Advisory: https://git.kernel.org/stable/c/056e8a46d79e22983bae4267e0d9c52927076f46
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution. 2. Reboot system to load new kernel.
🔧 Temporary Workarounds
Disable LLC module
linuxUnload LLC kernel module if not needed
sudo rmmod llc
Blacklist LLC module
linuxPrevent LLC module from loading at boot
echo 'blacklist llc' | sudo tee /etc/modprobe.d/blacklist-llc.conf
🧯 If You Can't Patch
- Restrict local user access to prevent untrusted users from running code
- Implement network filtering to block LLC protocol traffic if not needed
🔍 How to Verify
Check if Vulnerable:
Check kernel version and if LLC module is loaded: 'lsmod | grep llc'Check Version:
uname -rVerify Fix Applied:
Verify kernel version is patched and LLC module is either updated or disabled📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages in /var/log/kern.log or dmesg
- BUG_ON at net/core/skbuff.c:2178
Network Indicators:
- LLC protocol traffic to systems not expecting it
SIEM Query:
source="kernel" AND "BUG_ON" AND "skbuff.c:2178"🔗 References
- https://git.kernel.org/stable/c/056e8a46d79e22983bae4267e0d9c52927076f46
- https://git.kernel.org/stable/c/0f764208dc24ea043c3e20194d32aebf94f8459c
- https://git.kernel.org/stable/c/13f3f872627f0f27c31245524fc11367756240ad
- https://git.kernel.org/stable/c/17f86e25431ebc15aa9245ff156414fdad47822d
- https://git.kernel.org/stable/c/416e8b4c20c6398044e93008deefd563289f477d
- https://git.kernel.org/stable/c/64e6a754d33d31aa844b3ee66fb93ac84ca1565e
- https://git.kernel.org/stable/c/9b6f083db141ece0024be01526aa05aa978811cb
- https://git.kernel.org/stable/c/cd1c44327bbbd50fc24f2b38892f5f328b784d0f
- https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
- https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html
