CVE-2025-37959 - Vulnerability Details

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.

No CVSS v4.0

Attack Vector Local

Attack Complexity High

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Key SSVC decision points have not yet been added.

Vendors	Products
Linux	Linux Kernel

No data.

References

Link	Providers
https://git.kernel.org/stable/c/355b0526336c0bf2bf7feaca033568ede524f763
https://git.kernel.org/stable/c/9e15ef33ba39fb6d9d1f51445957f16983a9437a
https://git.kernel.org/stable/c/b37e54259cab4f78b53953d6f6268b85f07bef3e
https://git.kernel.org/stable/c/c4327229948879814229b46aa26a750718888503
https://git.kernel.org/stable/c/de1067cc8cf0e8c11ae20cbe5c467aef19d04ded
https://lore.kernel.org/linux-cve-announce/2025052004-CVE-2025-37959-1d15@gregkh/T
https://nvd.nist.gov/vuln/detail/CVE-2025-37959
https://www.cve.org/CVERecord?id=CVE-2025-37959

History

Mon, 14 Jul 2025 13:45:00 +0000

Type	Values Removed	Values Added
Metrics	epss `{'score': 0.00045}`	epss `{'score': 0.00037}`

Sat, 14 Jun 2025 14:45:00 +0000

Type	Values Removed	Values Added
Metrics	cvssV3_1 `{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}`	cvssV3_1 `{'score': 4.7, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H'}`

Thu, 22 May 2025 02:45:00 +0000

Type	Values Removed	Values Added
References		https://lore.kernel.org/linux-cve-announce/2025052004-CVE-2025-37959-1d15@gregkh/T https://nvd.nist.gov/vuln/detail/CVE-2025-37959 https://www.cve.org/CVERecord?id=CVE-2025-37959
Metrics	threat_severity `None`	cvssV3_1 `{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}` threat_severity `Moderate`

Tue, 20 May 2025 16:15:00 +0000

Type	Values Removed	Values Added
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.
Title		bpf: Scrub packet on bpf_redirect_peer
References		https://git.kernel.org/stable/c/355b0526336c0bf2bf7feaca033568ede524f763 https://git.kernel.org/stable/c/9e15ef33ba39fb6d9d1f51445957f16983a9437a https://git.kernel.org/stable/c/b37e54259cab4f78b53953d6f6268b85f07bef3e https://git.kernel.org/stable/c/c4327229948879814229b46aa26a750718888503 https://git.kernel.org/stable/c/de1067cc8cf0e8c11ae20cbe5c467aef19d04ded

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2025-05-20T16:01:52.547Z

Updated: 2025-05-26T05:24:35.172Z

Reserved: 2025-04-16T04:51:23.974Z

Link: CVE-2025-37959

Vulnrichment

No data.

NVD

Status : Awaiting Analysis

Published: 2025-05-20T16:15:34.143

Modified: 2025-05-21T20:24:58.133

Link: CVE-2025-37959

Redhat

Severity : Moderate

Publid Date: 2025-05-20T00:00:00Z

Links: CVE-2025-37959 - Bugzilla

Metrics

Attack Vector Local

Attack Complexity High

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

Affected Vendors & Products

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