CVE-2026-98794

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

ipvs: filter some flags received in the backup server

While the IPVS SYNC protocol is not secure by design

we can still protect the backup server from messages that

can wreak havoc.

This commit addresses problems from received connection flags

or their combinations. We now drop messages as follows:

1. the NO_CPORT+TEMPLATE combination allows lookups for normal

connections to hit template which can break in many ways.

While the master does not sync connections with NO_CPORT flag,

i.e. before they are established, we still accept NO_CPORT

without TEMPLATE.

2. ONE_PACKET: it is not sent by master, so we do not

expect it in backup. Before now it was ignored by

IP_VS_CONN_F_BACKUP_MASK for protocol v1 while protocol

v0 created connections that are not hashed and dropped

immediately. Better to apply the IP_VS_CONN_F_BACKUP_MASK

also to the flags from v0 messages for consistency with v1.