Description
In the Linux kernel, the following vulnerability has been resolved:

sctp: discard the rest of the packet on a stale-cookie error

When an association is in COOKIE-ECHOED state and the peer sends a
bundled [ERROR(Stale Cookie)][DATA] packet from one of its non-primary
addresses, processing the ERROR chunk takes the non-fatal stale-cookie
retry path sctp_sf_do_5_2_6_stale(), which queues
SCTP_CMD_DEL_NON_PRIMARY while keeping the association alive.
sctp_cmd_del_non_primary() removes every non-primary transport -
including the very transport this packet arrived on, which is still
referenced by the receive lookup and shared by all chunks of the
packet via chunk->transport.

sctp_assoc_rm_peer() does redirect asoc->peer.last_data_from away from
the removed transport, but right afterwards the bundled DATA chunk
makes sctp_assoc_bh_rcv() re-register
asoc->peer.last_data_from = chunk->transport unconditionally, undoing
the redirection with the just-removed transport.

Once the packet is done, the receive reference is dropped and the
transport is RCU-freed, while the surviving association keeps the
dangling last_data_from. A later FWD-TSN (or the delayed SACK timer)
makes sctp_gen_sack() dereference it (->param_flags and friends), and
sctp_make_sack()/sctp_outq_select_transport() may write to the freed
object and link it into the live transport list. This is a
use-after-free triggerable by any malicious SCTP peer (or a local
unprivileged user acting as one) with no capabilities required:

BUG: KASAN: slab-use-after-free in sctp_do_sm+0x498a/0x5660
Read of size 4 at addr ffff88800e1e356c by task poc/115
Call Trace: sctp_do_sm <- sctp_assoc_bh_rcv <- sctp_inq_push <-
sctp_rcv <- ip_protocol_deliver_rcu <- ip_rcv
Allocated: sctp_transport_new <- sctp_assoc_add_peer <-
sctp_process_init (INIT-ACK processing)
Freed: kfree <- sctp_transport_destroy_rcu <- rcu_core
(call_rcu queued by sctp_transport_put at end of sctp_rcv)
The buggy address is located 364 bytes inside of freed 1024-byte
region [ffff88800e1e3400, ffff88800e1e3800), cache kmalloc-1k

Note that commit 03a9d10ecf71 ("sctp: drop a chunk if its transport
was removed") only covers the window between the receive lookup and
the chunk processing (e.g. an ASCONF DEL-IP racing the socket backlog);
here the transport is removed *while* the packet is being processed,
by an earlier chunk of the same packet, so the drop in sctp_inq_push()
does not reach this path. Verified with the bundled [ERROR(Stale
Cookie)][DATA] + FWD-TSN reproducer: the KASAN report above still
fires with that commit applied, and is gone with this patch on top.

Fix it by discarding the rest of the packet on this path, as suggested
by Xin. After the stale-cookie ERROR has sent the association back to
COOKIE-WAIT and removed the non-primary transports, the remaining
chunks of the packet can only run against the restarted handshake
while referencing the removed arrival transport through
chunk->transport: besides the last_data_from registration above,
sctp_cmd_setup_t2() and the sctp_make_*() reply builders would also
copy that pointer into association-lifetime state that
sctp_assoc_rm_peer() has already sanitized. Let the peer retransmit
them, in line with what sctp_inq_push() does for chunks whose
transport was removed before processing.
Published: 2026-10-18
Score: n/a
EPSS: n/a
KEV: No
AI Analysis

Analysis and contextual insights are available on OpenCVE Cloud.

Remediation

No solution or workaround provided in the CVE record.

Additional remediation guidance may be available on OpenCVE Cloud.

Tracking

Sign in to view the affected projects.

Advisories

No advisories yet.

History

Sun, 18 Oct 2026 15:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: sctp: discard the rest of the packet on a stale-cookie error When an association is in COOKIE-ECHOED state and the peer sends a bundled [ERROR(Stale Cookie)][DATA] packet from one of its non-primary addresses, processing the ERROR chunk takes the non-fatal stale-cookie retry path sctp_sf_do_5_2_6_stale(), which queues SCTP_CMD_DEL_NON_PRIMARY while keeping the association alive. sctp_cmd_del_non_primary() removes every non-primary transport - including the very transport this packet arrived on, which is still referenced by the receive lookup and shared by all chunks of the packet via chunk->transport. sctp_assoc_rm_peer() does redirect asoc->peer.last_data_from away from the removed transport, but right afterwards the bundled DATA chunk makes sctp_assoc_bh_rcv() re-register asoc->peer.last_data_from = chunk->transport unconditionally, undoing the redirection with the just-removed transport. Once the packet is done, the receive reference is dropped and the transport is RCU-freed, while the surviving association keeps the dangling last_data_from. A later FWD-TSN (or the delayed SACK timer) makes sctp_gen_sack() dereference it (->param_flags and friends), and sctp_make_sack()/sctp_outq_select_transport() may write to the freed object and link it into the live transport list. This is a use-after-free triggerable by any malicious SCTP peer (or a local unprivileged user acting as one) with no capabilities required: BUG: KASAN: slab-use-after-free in sctp_do_sm+0x498a/0x5660 Read of size 4 at addr ffff88800e1e356c by task poc/115 Call Trace: sctp_do_sm <- sctp_assoc_bh_rcv <- sctp_inq_push <- sctp_rcv <- ip_protocol_deliver_rcu <- ip_rcv Allocated: sctp_transport_new <- sctp_assoc_add_peer <- sctp_process_init (INIT-ACK processing) Freed: kfree <- sctp_transport_destroy_rcu <- rcu_core (call_rcu queued by sctp_transport_put at end of sctp_rcv) The buggy address is located 364 bytes inside of freed 1024-byte region [ffff88800e1e3400, ffff88800e1e3800), cache kmalloc-1k Note that commit 03a9d10ecf71 ("sctp: drop a chunk if its transport was removed") only covers the window between the receive lookup and the chunk processing (e.g. an ASCONF DEL-IP racing the socket backlog); here the transport is removed *while* the packet is being processed, by an earlier chunk of the same packet, so the drop in sctp_inq_push() does not reach this path. Verified with the bundled [ERROR(Stale Cookie)][DATA] + FWD-TSN reproducer: the KASAN report above still fires with that commit applied, and is gone with this patch on top. Fix it by discarding the rest of the packet on this path, as suggested by Xin. After the stale-cookie ERROR has sent the association back to COOKIE-WAIT and removed the non-primary transports, the remaining chunks of the packet can only run against the restarted handshake while referencing the removed arrival transport through chunk->transport: besides the last_data_from registration above, sctp_cmd_setup_t2() and the sctp_make_*() reply builders would also copy that pointer into association-lifetime state that sctp_assoc_rm_peer() has already sanitized. Let the peer retransmit them, in line with what sctp_inq_push() does for chunks whose transport was removed before processing.
Title sctp: discard the rest of the packet on a stale-cookie error
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-10-18T15:18:16.510Z

Reserved: 2026-09-25T10:25:14.356Z

Link: CVE-2026-98548

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses

No weakness.