CVE-2025-22111
📋 TL;DR
A race condition vulnerability in the Linux kernel's bridge networking subsystem allows concurrent bridge operations to cause a deadlock or system instability. This affects Linux systems using bridge networking with SIOCBRADDIF/SIOCBRDELIF ioctl operations. Attackers with CAP_NET_ADMIN privileges can trigger this condition.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
System deadlock requiring reboot, causing denial of service and potential data loss in critical network operations.
Likely Case
Temporary network disruption, bridge interface failures, or kernel warning splats in system logs during concurrent bridge operations.
If Mitigated
Minimal impact with proper access controls limiting CAP_NET_ADMIN privileges and avoiding concurrent bridge modifications.
🎯 Exploit Status
Exploitation requires CAP_NET_ADMIN privileges and precise timing of concurrent bridge operations. The vulnerability is a race condition rather than a memory corruption issue.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits 00fe0ac64efd1f5373b3dd9f1f84b19235371e39, 338a0f3c66aef4ee13052880d02200aae8f2d8a8, 4888e1dcc341e9a132ef7b8516234b3c3296de56, d767ce15045df510f55cdd2af5df0eee71f928d0, or ed3ba9b6e280e14cc3148c1b226ba453f02fa76c
Vendor Advisory: https://git.kernel.org/stable/c/00fe0ac64efd1f5373b3dd9f1f84b19235371e39
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution vendor. 2. Check kernel changelog for the specific fix commits. 3. Reboot system to load new kernel.
🔧 Temporary Workarounds
Restrict CAP_NET_ADMIN Privileges
linuxLimit users and processes with CAP_NET_ADMIN capability to reduce attack surface.
# Review capabilities: capsh --print
# Remove CAP_NET_ADMIN: setcap cap_net_admin-ep /path/to/binary
# Use namespaces to isolate network privileges
Avoid Concurrent Bridge Operations
linuxImplement locking or serialization for bridge configuration changes.
# Use flock for script serialization: flock -x /var/lock/bridge.lock brctl delif br0 eth0
# Implement queueing for bridge management operations
🧯 If You Can't Patch
- Implement strict access controls to limit CAP_NET_ADMIN privileges to essential users/processes only.
- Monitor system logs for bridge-related warnings and implement alerting for potential deadlock conditions.
🔍 How to Verify
Check if Vulnerable:
Check kernel version and verify if fix commits are present: grep -E '00fe0ac64efd1f5373b3dd9f1f84b19235371e39|338a0f3c66aef4ee13052880d02200aae8f2d8a8|4888e1dcc341e9a132ef7b8516234b3c3296de56|d767ce15045df510f55cdd2af5df0eee71f928d0|ed3ba9b6e280e14cc3148c1b226ba453f02fa76c' /lib/modules/$(uname -r)/build/.configCheck Version:
uname -rVerify Fix Applied:
After patching, verify kernel version includes fix: uname -r and check distribution changelog for fix commits.📡 Detection & Monitoring
Log Indicators:
- Kernel messages containing 'unregister_netdevice: waiting for [interface] to become free'
- Refcount tracker warnings in dmesg or /var/log/kern.log
- Bridge-related error messages in system logs
Network Indicators:
- Unexpected bridge interface failures
- Network connectivity loss in bridged environments
SIEM Query:
source="kernel" AND ("unregister_netdevice" OR "Usage count" OR "ref_tracker")🔗 References
- https://git.kernel.org/stable/c/00fe0ac64efd1f5373b3dd9f1f84b19235371e39
- https://git.kernel.org/stable/c/338a0f3c66aef4ee13052880d02200aae8f2d8a8
- https://git.kernel.org/stable/c/4888e1dcc341e9a132ef7b8516234b3c3296de56
- https://git.kernel.org/stable/c/d767ce15045df510f55cdd2af5df0eee71f928d0
- https://git.kernel.org/stable/c/ed3ba9b6e280e14cc3148c1b226ba453f02fa76c
- https://git.kernel.org/stable/c/f51e471cb1577d510c3096e126678e1ea20d2efd
