CVE-2026-98952: pfcp: make sure the SEID is linear before reading it
In the Linux kernel, the following vulnerability has been resolved:
pfcp: make sure the SEID is linear before reading it
pfcpencaprecv() only makes sure that the UDP header and the 4 byte PFCP header are in the linear area. When the S flag is set, pfcpsessionrecv() then reads the 8 byte SEID that follows, which is not covered by the pskbmaypull() check.
A short PFCP packet with the S flag set, or one whose session header lies in a fragment, therefore makes pfcpsessionrecv() 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 pskbmaypull() may reallocate the skb head.
Use offsetofend() rather than sizeof(struct pfcphdrsession): 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
In PFCP receive handling, ensure the 8-byte SEID is linear before reading it by pulling the skb through the end of the SEID, check packet length using offsetofend() rather than sizeof(struct pfcphdr_session), drop packets too short to contain the SEID, and reload the header pointer afterward because pskb_may_pull() may reallocate the skb head.