CVE-2026-89478 sctp: drop a chunk if its transport was removed
A use-after-free vulnerability in the Linux kernel SCTP implementation allows attackers to cause denial of service or potentially execute code via crafted packets.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89478?
CVE-2026-89478 is a critical use after free vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
sctp: drop a chunk if its transport was removed
sctp_rcv() resolves the transport once per packet and leaves it in chunk->transport. The lookup reference, or the one sctp_add_backlog() takes if the socket is owned by userspace, keeps it around until the chunk has been processed.
An authenticated ASCONF DEL-IP can remove it in the meantime. sctp_assoc_rm_peer() takes the transport out of the association and calls sctp_transport_free(), which tags it dead and drops the reference the association held. There is a window on both paths: the packet can sit on the socket backlog, and on the direct path the lookup completes before bh_lock_sock().
The DATA chunk in that packet puts the removed transport back into asoc->peer.last_data_from. Once the packet is done that reference goes away and the transport is freed by RCU, so the next delayed SACK carries the pointer into the SACK chunk and sctp_outq_select_transport() reads the freed transport's state.
Drop the chunk in sctp_inq_push(), next to the existing rcvr->dead check. Both paths reach it with the association's socket lock held. The peer retransmits it.
Which versions are affected by CVE-2026-89478?
How do I fix CVE-2026-89478?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-89478 being exploited?
There is no known exploitation of CVE-2026-89478 in the wild and no public exploit code.
Sources
Also known as AZL-100127, BELL-CVE-2026-89478, DEBIAN-CVE-2026-89478, GHSA-47r2-m88p-rgjm, UBUNTU-CVE-2026-89478.