CVE-2026-98952

In the Linux kernel, the following vulnerability has been resolved:

pfcp: make sure the SEID is linear before reading it

pfcp encap recv() only makes sure that the UDP header and the 4 byte PFCP header are in the linear area. When the S flag is set, pfcp session recv() then reads the 8 byte SEID that follows, which is not covered by the pskb may pull() check.

A short PFCP packet with the S flag set, or one whose session header lies in a fragment, therefore makes pfcp session recv() read beyond the end of the packet data, and whatever it finds there is stored in the tunnel metadata that flower later classifies on.

Pull up to the end of the SEID before reading it, and drop packets that are too short to contain it. Reload the header pointer afterwards since pskb may pull() may reallocate the skb head.

Use offsetofend() rather than sizeof(struct pfcphdr session): the structure is not packed, so its size is 16 bytes because of the alignment of the be64 member, while the header on the wire is only 12 bytes, and valid session messages would be dropped.