CVE-2026-72398

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

sctp: add INIT verification after cookie unpacking

In SCTP handshake, the INIT chunk is initially processed by the server

and embedded into the cookie carried in INIT-ACK. The client then

returns this cookie via COOKIE-ECHO, where the server unpacks it and

reconstructs the original INIT chunk.

When cookie authentication is enabled, the cookie contents are protected

against tampering, so reusing the unpacked INIT without re-verification

is safe.

However, when cookie authentication is disabled, the reconstructed INIT

can no longer be trusted. In this case, the INIT must be explicitly

validated after unpacking to avoid processing potentially tampered data.

Add sctp_verify_init() checks after cookie unpacking in COOKIE-ECHO

processing paths (sctp_sf_do_5_1D_ce() and sctp_sf_do_5_2_4_dupcook())

when cookie_auth_enable is disabled. On failure, the new association is

freed and the packet is discarded.

Also tighten cookie validation in sctp_unpack_cookie() by verifying the

embedded chunk type is SCTP_CID_INIT before treating it as an INIT

chunk.

Finally, update sctp_verify_init() to validate parameter bounds using

the actual embedded INIT length instead of chunk->chunk_end, since the

INIT stored in COOKIE-ECHO may not span the entire chunk buffer.