UBUNTU-CVE-2025-40183
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.
02 / AFFECTED SOFTWARE
Affected packages
11 explicit affected versions
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39 explicit affected versions
13 explicit affected versions
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28 explicit affected versions
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45 explicit affected versions
37 explicit affected versions
44 explicit affected versions
14 explicit affected versions
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9 explicit affected versions
9 explicit affected versions
11 explicit affected versions
32 explicit affected versions
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81 explicit affected versions
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1 explicit affected versions
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1 explicit affected versions
79 explicit affected versions
70 explicit affected versions
69 explicit affected versions
13 explicit affected versions
43 explicit affected versions
6 explicit affected versions
10 explicit affected versions
8 explicit affected versions
38 explicit affected versions
14 explicit affected versions
4 explicit affected versions
78 explicit affected versions
6 explicit affected versions
11 explicit affected versions
1 explicit affected versions
12 explicit affected versions
32 explicit affected versions
69 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/23f3770e1a53e6c7a553135011f547209e141e72
- https://git.kernel.org/stable/c/057764172fcc6ee2ccb6c41351a55a9f054dc8fd
- https://git.kernel.org/stable/c/23f3770e1a53e6c7a553135011f547209e141e72
- https://git.kernel.org/stable/c/2e67c2037382abb56497bb9d7b7e10be04eb5598
- https://git.kernel.org/stable/c/3fba965a9aac0fa3cbd8138436a37af9ab466d79
- https://git.kernel.org/stable/c/7404ce888a45eb7da0508b7cbbe6f2e95302eeb8
- https://git.kernel.org/stable/c/b6bfe44b6dbb14a31d86c475cdc9c7689534fb09
- https://git.kernel.org/stable/c/f36a305d30f557306d87c787ddffe094ac5dac89
- https://ubuntu.com/security/CVE-2025-40183
- https://ubuntu.com/security/notices/USN-8029-1
- https://ubuntu.com/security/notices/USN-8029-2
- https://ubuntu.com/security/notices/USN-8029-3
- https://ubuntu.com/security/notices/USN-8030-1
- https://ubuntu.com/security/notices/USN-8033-1
- https://ubuntu.com/security/notices/USN-8033-2
- https://ubuntu.com/security/notices/USN-8033-3
- https://ubuntu.com/security/notices/USN-8033-4
- https://ubuntu.com/security/notices/USN-8033-5
- https://ubuntu.com/security/notices/USN-8033-6
- https://ubuntu.com/security/notices/USN-8033-7
- https://ubuntu.com/security/notices/USN-8033-8
- https://ubuntu.com/security/notices/USN-8034-1
- https://ubuntu.com/security/notices/USN-8034-2
- https://ubuntu.com/security/notices/USN-8048-1
- https://ubuntu.com/security/notices/USN-8095-1
- https://ubuntu.com/security/notices/USN-8095-2
- https://ubuntu.com/security/notices/USN-8095-3
- https://ubuntu.com/security/notices/USN-8095-4
- https://ubuntu.com/security/notices/USN-8095-5
- https://ubuntu.com/security/notices/USN-8100-1
- https://ubuntu.com/security/notices/USN-8125-1
- https://ubuntu.com/security/notices/USN-8126-1
- https://ubuntu.com/security/notices/USN-8141-1
- https://ubuntu.com/security/notices/USN-8163-1
- https://ubuntu.com/security/notices/USN-8163-2
- https://ubuntu.com/security/notices/USN-8165-1
- https://ubuntu.com/security/notices/USN-8243-1
- https://ubuntu.com/security/notices/USN-8261-1
- https://www.cve.org/CVERecord?id=CVE-2025-40183