CVE-2025-22021
Linux Kernel vulnerability
- Published16 Apr 2025
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.
CVSS 3.1 breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:HAffected products
Remediation
- https://git.kernel.org/stable/c/1ca2169cc19dca893c7aae6af122852097435d16
- https://git.kernel.org/stable/c/1ec43100f7123010730b7ddfc3d5c2eac19e70e7
- https://git.kernel.org/stable/c/221c27259324ec1404f028d4f5a0f2ae7f63ee23
- https://git.kernel.org/stable/c/2bb139e483f8cbe488d19d8c1135ac3615e2668c
- https://git.kernel.org/stable/c/41904cbb343d115931d6bf79aa2c815cac4ef72b
- https://git.kernel.org/stable/c/5251041573850e5020cd447374e23010be698898
References
- https://git.kernel.org/stable/c/1ca2169cc19dca893c7aae6af122852097435d16
- https://git.kernel.org/stable/c/1ec43100f7123010730b7ddfc3d5c2eac19e70e7
- https://git.kernel.org/stable/c/221c27259324ec1404f028d4f5a0f2ae7f63ee23
- https://git.kernel.org/stable/c/2bb139e483f8cbe488d19d8c1135ac3615e2668c
- https://git.kernel.org/stable/c/41904cbb343d115931d6bf79aa2c815cac4ef72b
- https://git.kernel.org/stable/c/5251041573850e5020cd447374e23010be698898
- https://git.kernel.org/stable/c/58ab63d3ded2ca6141357a2b24eee8453d0f871d
- https://git.kernel.org/stable/c/6488b96a79a26e19100ad872622f04e93b638d7f
- https://git.kernel.org/stable/c/932b32ffd7604fb00b5c57e239a3cc4d901ccf6e
- https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
and 1 more references
Frequently asked
Is CVE-2025-22021 being actively exploited?
CVE-2025-22021 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.46%.
How severe is CVE-2025-22021?
CVE-2025-22021 has a CVSS 3.1 base score of 10.0, rated critical. EPSS estimates a 0.46% probability of exploitation.
Which products are affected by CVE-2025-22021?
Affected products include Linux Kernel.
How do I fix CVE-2025-22021?
Upgrade affected software to a fixed version, for example Linux Kernel 5.4.292 or later, then confirm no affected versions remain in your inventory.
How Secuno handles this
Secuno correlates vulnerabilities like CVE-2025-22021 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.
Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.