Threats Tagged 'cve-2025-40183'

A vulnerability in the Linux kernel related to the bpf_redirect_neigh() helper caused a memory leak of metadata_dst objects in the kernel's kmalloc-256 slab. This issue affected the BPF egress gateway feature used by Cilium for Kubernetes pod traffic, where vxlan tunnels allocate metadata_dst objects that were not properly released. The leak occurs because bpf_redirect_neigh() sets a new destination entry without releasing the previous one, leading to increasing kernel memory usage over time.

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix metadata_dst leak __bpf_redirect_neigh_v{4,6} Cilium has a BPF egress gateway feature which forces outgoing K8s Pod traffic to pass through dedicated egress gateways which then SNAT the traffic in order to interact with stable IPs outside the cluster. The traffic is directed to the gateway via vxlan tunnel in collect md mode. A recent BPF change utilized the bpf_redirect_neigh() helper to forward packets after the arrival and decap on vxlan, which turned out over time that the kmalloc-256 slab usage in kernel was ever-increasing. The issue was that vxlan allocates the metadata_dst object and attaches it through a fake dst entry to the skb. The latter was never released though given bpf_redirect_neigh() was merely setting the new dst entry via skb_dst_set() without dropping an existing one first.