CVE-2026-89478

sctp: drop a chunk if its transport was removed

Published Sep 11, 2026 CVSS 3.1 · 9.8 Critical EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4817-1 linux-6.12 security update
Debian DLA Debian DLA DLA-4841-1 linux security update
Debian DSA Debian DSA DSA-6528-1 linux security update
Ubuntu USN Ubuntu USN USN-8961-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9002-1 Linux kernel (NVIDIA Tegra) vulnerabilities
Ubuntu USN Ubuntu USN USN-9019-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9020-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9022-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9023-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9024-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9025-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9026-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9029-1 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-9039-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-9040-1 Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9066-1 Linux kernel (HWE) vulnerabilities
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H'}

cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

Type Values Removed Values Added
Weaknesses CWE-825
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H'}

threat_severity

Important

Type Values Removed Values Added
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.
Title sctp: drop a chunk if its transport was removed
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 19, 2026, 8:47 AM
Reserved
Sep 11, 2026, 7:38 PM
Status
Received
Published
Sep 11, 2026, 8:19 PM
Modified
Oct 19, 2026, 9:17 AM
Severity
Important
Public date
Sep 11, 2026, 7:43 PM