CVE-2026-89478: Linux Vulnerability (CVSS 9.8)

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.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

0.46%

38.8th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 3fc072e7cb4a0ff251d13cfc2d24f62489cd9386; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < d7cb5ad832095dc4becfdb2a36007ffd50e49fb0; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 0422b092a3d43ca462932ff9f747731ca078d1d4; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 928fd7920ba37cc5637a211b9be979083413a2fa; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < c6c86a5e62a4fec36692ddd64b9144b660f71f96; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 1035bdef1efb9b1076d1a57b81e08c637ff08ecc; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 3537961df2163258bddc230db0e18dc14e925ea6; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 03a9d10ecf71f54b2af8020935f2033d4a132be5
Linux	Linux	2.6.12

References

Timeline

Published: Sep 11, 2026
Last Modified: Sep 14, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-89478?

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.

How severe is CVE-2026-89478?

CVE-2026-89478 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.46% probability of exploitation in the next 30 days.

How do I fix CVE-2026-89478?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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