CVE-2026-74586

A flaw was found in the Linux kernel's Stream Control Transmission Protocol (SCTP) implementation. An authenticated remote SCTP peer can trigger a use-after-free vulnerability by adding and then immediately removing a transport within the same ASCONF chunk. This can lead to a system crash, resulting in a denial of service.

An SCTP use-after-free can occur when an authenticated remote peer sends an ASCONF chunk that adds a new transport and then removes it with a wildcard DEL-IP operation. The removed transport can remain referenced by asoc->new_transport and later be attached to a queued HEARTBEAT without a valid transport reference. After RCU frees the transport, subsequent ASCONF_ACK processing can reach sctp_outq_select_transport() and dereference the freed object. The upstream reproducer reliably triggered a KASAN slab-use-after-free while reading transport->state.

Exploitation requires an existing SCTP association with an authenticated peer capable of ASCONF dynamic address reconfiguration and a specific multi-stage sequence, increasing practical attack complexity. For CVSS, AV:N reflects that the trigger originates from a remote SCTP peer, while PR:L reflects the required authenticated peer context rather than arbitrary unauthenticated network access.

The demonstrated impact is a kernel use-after-free read that can cause a kernel crash and denial of service. Confidentiality or integrity impact is possible as a paranoid worst case because a freed kernel networking object is accessed, but should not be considered confirmed impact.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue on systems where the SCTP protocol is not needed, prevent the sctp kernel module from loading:

1. Add the module configuration to prevent loading:

echo "install sctp /bin/true" > /etc/modprobe.d/sctp-disable.conf

2. Unload the module from the active system if loaded:

modprobe -r sctp

Warning: If the sctp module is currently in use, unloading will fail and a system reboot will be required to apply the changes. Disabling this module will cause any applications requiring SCTP networking functionality to fail.