CVE-2025-22021
Kubernetes Cilium Envoy IPv6 SNAT Socket Vulnerability
Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: socket: Lookup orig tuple for IPv6 SNAT nf_sk_lookup_slow_v4 does the conntrack lookup for IPv4 packets to restore the original 5-tuple in case of SNAT, to be able to find the right socket (if any). Then socket_match() can correctly check whether the socket was transparent. However, the IPv6 counterpart (nf_sk_lookup_slow_v6) lacks this conntrack lookup, making xt_socket fail to match on the socket when the packet was SNATed. Add the same logic to nf_sk_lookup_slow_v6. IPv6 SNAT is used in Kubernetes clusters for pod-to-world packets, as pods' addresses are in the fd00::/8 ULA subnet and need to be replaced with the node's external address. Cilium leverages Envoy to enforce L7 policies, and Envoy uses transparent sockets. Cilium inserts an iptables prerouting rule that matches on `-m socket --transparent` and redirects the packets to localhost, but it fails to match SNATed IPv6 packets due to that missing conntrack lookup.
INFO
Published Date :
April 16, 2025, 11:15 a.m.
Last Modified :
April 16, 2025, 1:25 p.m.
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Remotely Exploitable :
No
Impact Score :
Exploitability Score :
References to Advisories, Solutions, and Tools
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CVE-2025-22021.
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Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Apr. 16, 2025
Action Type Old Value New Value Added Description In the Linux kernel, the following vulnerability has been resolved: netfilter: socket: Lookup orig tuple for IPv6 SNAT nf_sk_lookup_slow_v4 does the conntrack lookup for IPv4 packets to restore the original 5-tuple in case of SNAT, to be able to find the right socket (if any). Then socket_match() can correctly check whether the socket was transparent. However, the IPv6 counterpart (nf_sk_lookup_slow_v6) lacks this conntrack lookup, making xt_socket fail to match on the socket when the packet was SNATed. Add the same logic to nf_sk_lookup_slow_v6. IPv6 SNAT is used in Kubernetes clusters for pod-to-world packets, as pods' addresses are in the fd00::/8 ULA subnet and need to be replaced with the node's external address. Cilium leverages Envoy to enforce L7 policies, and Envoy uses transparent sockets. Cilium inserts an iptables prerouting rule that matches on `-m socket --transparent` and redirects the packets to localhost, but it fails to match SNATed IPv6 packets due to that missing conntrack lookup. Added Reference https://git.kernel.org/stable/c/1ca2169cc19dca893c7aae6af122852097435d16 Added Reference https://git.kernel.org/stable/c/1ec43100f7123010730b7ddfc3d5c2eac19e70e7 Added Reference https://git.kernel.org/stable/c/221c27259324ec1404f028d4f5a0f2ae7f63ee23 Added Reference https://git.kernel.org/stable/c/2bb139e483f8cbe488d19d8c1135ac3615e2668c Added Reference https://git.kernel.org/stable/c/41904cbb343d115931d6bf79aa2c815cac4ef72b Added Reference https://git.kernel.org/stable/c/5251041573850e5020cd447374e23010be698898 Added Reference https://git.kernel.org/stable/c/58ab63d3ded2ca6141357a2b24eee8453d0f871d Added Reference https://git.kernel.org/stable/c/6488b96a79a26e19100ad872622f04e93b638d7f Added Reference https://git.kernel.org/stable/c/932b32ffd7604fb00b5c57e239a3cc4d901ccf6e
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-22021 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-22021
weaknesses.