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

sctp: fix NULL deref on untransmitted RECONF completion

sctp_process_strreset_outreq(), sctp_process_strreset_addstrm_out() and
sctp_process_strreset_resp() complete a pending stream reconfiguration
request by stopping the reconf timer on the transport it was sent on:

t = asoc->strreset_chunk->transport;
if (timer_delete(&t->reconf_timer))
sctp_transport_put(t);

chunk->transport is assigned by __sctp_packet_append_chunk() when the
chunk is appended to an outbound packet, and sctp_outq_flush_ctrl() arms
the reconf timer at that same point. A request already published in
asoc->strreset_chunk but not yet transmitted has neither, so completing
it dereferences NULL.

Two ways to get there. sctp_send_asconf_del_ip() sets
asoc->src_out_of_asoc_ok without sending anything when the address being
removed is the association's last one, and sctp_outq_flush_ctrl() then
leaves every non-ASCONF control chunk queued; as only
sctp_process_asconf_ack() clears that flag, it persists. An unprivileged
process that removes such an address and then asks for a stream reset
panics the kernel from softirq. A peer needs neither ASCONF nor local
help: sctp_cmd_interpreter() uncorks the outqueue only once the whole
packet has been processed, so a reply built while walking a RECONF chunk
stays untransmitted for the rest of that walk, and one RECONF chunk
carrying [Incoming SSN Reset Request, Outgoing SSN Reset Request,
Response] -- or two RECONF chunks in one packet -- reaches the same
dereference.

KASAN: null-ptr-deref in range [0x00000000000001e8-0x00000000000001ef]
RIP: 0010:timer_delete+0x67/0x110
Call Trace:
<IRQ>
sctp_process_strreset_addstrm_out (net/sctp/stream.c:832)
sctp_sf_do_reconf (net/sctp/sm_statefuns.c:4212)
sctp_do_sm (net/sctp/sm_sideeffect.c:1172)
sctp_assoc_bh_rcv (net/sctp/associola.c:1044)
sctp_rcv (net/sctp/input.c:243)
ip_local_deliver (net/ipv4/ip_input.c:262)
process_backlog (net/core/dev.c:6680)
</IRQ>

A response can only acknowledge a request that was actually sent, so do
not match asoc->strreset_chunk while chunk->transport is NULL. Guarding
the lookup covers all three completion sites.
Published: 2026-09-11
Score: 5.9 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Sat, 12 Sep 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-476
References
Metrics threat_severity

None

 cvssV3_1

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

threat_severity

Important

Fri, 11 Sep 2026 23:45:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: sctp: fix NULL deref on untransmitted RECONF completion sctp_process_strreset_outreq(), sctp_process_strreset_addstrm_out() and sctp_process_strreset_resp() complete a pending stream reconfiguration request by stopping the reconf timer on the transport it was sent on: t = asoc->strreset_chunk->transport; if (timer_delete(&t->reconf_timer)) sctp_transport_put(t); chunk->transport is assigned by __sctp_packet_append_chunk() when the chunk is appended to an outbound packet, and sctp_outq_flush_ctrl() arms the reconf timer at that same point. A request already published in asoc->strreset_chunk but not yet transmitted has neither, so completing it dereferences NULL. Two ways to get there. sctp_send_asconf_del_ip() sets asoc->src_out_of_asoc_ok without sending anything when the address being removed is the association's last one, and sctp_outq_flush_ctrl() then leaves every non-ASCONF control chunk queued; as only sctp_process_asconf_ack() clears that flag, it persists. An unprivileged process that removes such an address and then asks for a stream reset panics the kernel from softirq. A peer needs neither ASCONF nor local help: sctp_cmd_interpreter() uncorks the outqueue only once the whole packet has been processed, so a reply built while walking a RECONF chunk stays untransmitted for the rest of that walk, and one RECONF chunk carrying [Incoming SSN Reset Request, Outgoing SSN Reset Request, Response] -- or two RECONF chunks in one packet -- reaches the same dereference. KASAN: null-ptr-deref in range [0x00000000000001e8-0x00000000000001ef] RIP: 0010:timer_delete+0x67/0x110 Call Trace: <IRQ> sctp_process_strreset_addstrm_out (net/sctp/stream.c:832) sctp_sf_do_reconf (net/sctp/sm_statefuns.c:4212) sctp_do_sm (net/sctp/sm_sideeffect.c:1172) sctp_assoc_bh_rcv (net/sctp/associola.c:1044) sctp_rcv (net/sctp/input.c:243) ip_local_deliver (net/ipv4/ip_input.c:262) process_backlog (net/core/dev.c:6680) </IRQ> A response can only acknowledge a request that was actually sent, so do not match asoc->strreset_chunk while chunk->transport is NULL. Guarding the lookup covers all three completion sites.
Title sctp: fix NULL deref on untransmitted RECONF completion
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: 2026-09-11T19:43:33.851Z

Reserved: 2026-09-11T19:38:34.711Z

Link: CVE-2026-89477

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-11T20:19:29.063

Modified: 2026-09-11T20:19:29.063

Link: CVE-2026-89477

cve-icon Redhat

Severity : Important

Publid Date: 2026-09-11T19:43:33Z

Links: CVE-2026-89477 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-12T04:00:07Z

Weaknesses