CVE-2025-38248
📋 TL;DR
A use-after-free vulnerability in the Linux kernel's bridge multicast implementation allows attackers to potentially crash the kernel or execute arbitrary code. This affects systems using Linux bridges with VLAN filtering and multicast snooping enabled. Attackers with local network access could exploit this to gain elevated privileges or cause denial of service.
💻 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 →⚠️ Risk & Real-World Impact
Worst Case
Kernel panic leading to system crash, or potential arbitrary code execution with kernel privileges resulting in complete system compromise.
Likely Case
Kernel crash or instability causing denial of service on affected systems, potentially disrupting network connectivity.
If Mitigated
Limited impact if proper network segmentation and access controls prevent unauthorized access to bridge configuration.
🎯 Exploit Status
Exploitation requires network configuration privileges and specific bridge setup. The vulnerability involves complex multicast router list management.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions with fixes from git commits: 4d3c2a1d4c7c33103f1ddfdbc5cfe1ea4f6d0dcd, 7544f3f5b0b58c396f374d060898b5939da31709, bdced577da71b118b6ed4242ebd47f81bf54d406, f05a4f9e959e0fc098046044c650acf897ea52d2
Vendor Advisory: https://git.kernel.org/stable/c/4d3c2a1d4c7c33103f1ddfdbc5cfe1ea4f6d0dcd
Restart Required: Yes
Instructions:
1. Update Linux kernel to patched version from your distribution. 2. Check kernel version with 'uname -r'. 3. Reboot system to load new kernel. 4. Verify bridge functionality post-update.
🔧 Temporary Workarounds
Disable vulnerable bridge features
linuxDisable VLAN filtering or multicast snooping on bridges to prevent triggering the vulnerability
ip link set dev <bridge_name> type bridge vlan_filtering 0
ip link set dev <bridge_name> type bridge mcast_snooping 0
Avoid per-VLAN multicast configuration changes
linuxDo not modify mcast_router settings or mcast_vlan_snooping while bridge ports are configured
🧯 If You Can't Patch
- Implement strict network segmentation to limit access to bridge configuration interfaces
- Monitor bridge configuration changes and audit logs for unauthorized modifications
🔍 How to Verify
Check if Vulnerable:
Check if bridge has VLAN filtering and multicast snooping enabled: 'bridge link show | grep -A5 <bridge_name>' and look for 'vlan_filtering 1' and 'mcast_snooping 1'Check Version:
uname -rVerify Fix Applied:
After patching, test the specific scenarios described in the CVE: configure bridge with vlan_filtering=1, mcast_snooping=1, add ports, modify mcast_router settings, and check for stability📡 Detection & Monitoring
Log Indicators:
- Kernel panic messages
- KASAN slab-out-of-bounds errors in dmesg
- Bridge multicast router list corruption warnings
Network Indicators:
- Unexpected bridge port behavior
- Multicast forwarding failures
- Network connectivity loss on bridged interfaces
SIEM Query:
source="kernel" AND ("KASAN" OR "slab-out-of-bounds" OR "bridge" OR "multicast")