CVE-2026-89479
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
A use-after-free vulnerability exists in the Linux kernel's SCTP handling. A remote peer can bundle COOKIE ECHO, SHUTDOWN and SHUTDOWN ACK chunks in a single packet, causing the association and its transports to be freed, after which the endpoint loop writes to freed memory. This occurs when the packet is processed from the socket backlog in task context.
Risk Assessment
The vulnerability can lead to kernel memory corruption, system crash (panic), or potentially remote code execution by an attacker sending crafted SCTP packets. It affects systems with SCTP enabled that are reachable over the network.
Recommendation
Update the Linux kernel to a version containing the fix for CVE-2026-89479. If SCTP is not used, consider disabling or blocking the protocol at the firewall.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: sctp: stop processing a packet once its association is deleted sctp_endpoint_bh_rcv() looks the association up only when chunk->asoc is NULL, and caches the result in chunk->asoc and chunk->transport without taking a reference. A packet that matches no association is handed to the endpoint, so a peer can bundle COOKIE ECHO, SHUTDOWN and SHUTDOWN ACK in one packet. The COOKIE ECHO creates the association, the SHUTDOWN chunk caches it, and with the outqueue empty the SHUTDOWN ACK reaches sctp_sf_do_9_2_final(), so the association and its transports are freed. The endpoint loop has no counterpart to the asoc->base.dead check in sctp_assoc_bh_rcv(). The next chunk writes to last_time_heard in the freed transport and is then passed to sctp_do_sm() with the freed association. The transport is freed through RCU, so this needs the packet to come off the socket backlog, where the loop runs in task context. The endpoint loop cannot do the same check: it holds no reference on the association, so reading asoc->base.dead would itself be a use-after-free. Mark the packet for discard in the command interpreter, just before it deletes the association. That is also before sctp_inq_free() releases the chunk on the association receive path. sctp_sf_do_5_2_4_dupcook() issues SCTP_CMD_DELETE_TCB for the temporary association, while the one the packet belongs to stays alive. A restarting peer can bundle DATA behind its COOKIE ECHO, so compare against chunk->asoc and leave that case alone.