CVE-2021-47160: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-47160 affects the Linux kernel's mt7530 driver in the DSA (Distributed Switch Architecture) subsystem. The vulnerability was discovered and disclosed in March 2024. The issue involves a VLAN traffic leak vulnerability where the PCR_MATRIX field was set to all 1's when VLAN filtering is enabled but was not reset when disabled (Kernel Git).

The vulnerability occurs in the mt7530_port_set_vlan_aware function within the mt7530 driver. When VLAN filtering is enabled, the PCR_MATRIX field is set to ALL_MEMBERS, but this setting persists even after VLAN filtering is disabled. This misconfiguration allows traffic to leak between different VLANs that should be isolated (Kernel Git).

When exploited, this vulnerability allows traffic to leak between different bridge interfaces that should be isolated. For example, when two bridges (br0 and br1) are created with VLAN filtering initially enabled and then disabled, traffic between br0 and br1 will start leaking to each other, compromising network isolation (Kernel Git).

The vulnerability can be triggered through a specific sequence of network configuration commands: creating bridges with VLAN filtering enabled, adding ports to different bridges, and then disabling VLAN filtering. This makes it relatively straightforward to exploit in environments where an attacker has the ability to configure network bridges (Kernel Git).

The issue has been fixed by removing the PCR_MATRIX write from mt7530_port_set_vlan_aware function, as port_bridge_{add,del} functions already handle PCR_MATRIX properly. Users should update to a patched version of the Linux kernel that includes this fix (Kernel Git).