bpf: Fix metadata_dst leak __bpf_redirect_neigh_v{4,6}
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 4 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.10.246, 5.15.195, 6.1.157, 6.6.113, 6.12.54, 6.17.4, 6.18
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
Not affected: 1 product
- Red Hat Enterprise Linux 7
Timeline
- 2026-10-02 Threatist record created from CVE-2025-40183
- 2026-10-03 Alias added: GHSA-553v-hjpm-738q
- 2026-10-16 CISA SSVC decision points changed
- 2026-10-16 Priority changed: LOW → MEDIUM
- 2026-11-04 EPSS moved to the 50th–90th percentile
References
Other 7
- https://git.kernel.org/stable/c/3fba965a9aac0fa3cbd8138436a37af9ab466d79
- https://git.kernel.org/stable/c/057764172fcc6ee2ccb6c41351a55a9f054dc8fd
- https://git.kernel.org/stable/c/2e67c2037382abb56497bb9d7b7e10be04eb5598
- https://git.kernel.org/stable/c/b6bfe44b6dbb14a31d86c475cdc9c7689534fb09
- https://git.kernel.org/stable/c/f36a305d30f557306d87c787ddffe094ac5dac89
- https://git.kernel.org/stable/c/7404ce888a45eb7da0508b7cbbe6f2e95302eeb8
- https://git.kernel.org/stable/c/23f3770e1a53e6c7a553135011f547209e141e72
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Sources
- CVE-2025-40183 · CVE Program
- CVE-2025-40183 · NVD
- FIRST EPSS
- GHSA-553v-hjpm-738q · GitHub Advisory Database · CC BY 4.0
- CVE-2025-40183 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences