CVE Catalog

CVE-2025-40183

HighCVSS 7.5
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.57%

44th percentile - higher than 44% of all known CVEs

Summary

In the Linux kernel, a metadata_dst leak was found in __bpf_redirect_neigh_v{4,6} functions. The issue occurs when BPF uses bpf_redirect_neigh() to forward packets after VXLAN decap in collect md mode. VXLAN allocates metadata_dst and attaches it via a fake dst entry to the skb, but bpf_redirect_neigh() sets a new dst entry via skb_dst_set() without dropping the existing one first, leading to an ever-increasing memory leak.

Risk Assessment

The kernel memory leak can eventually exhaust memory (especially in the kmalloc-256 slab), causing a denial of service (DoS) on the system.

Recommendation

Update the Linux kernel to a version containing the fix that properly releases the metadata_dst.

Other vulnerabilities in Linux kernel

See all
Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS