---
id: CVE-2026-89477
title: 'sctp: fix NULL deref on untransmitted RECONF completion'
summary: |-
  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…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-476
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 81054476453640159149cb6704e834893e16736b <
    79ff751311e80fa0370007e46a79a6d601685e75
  - >-
    Linux >= 81054476453640159149cb6704e834893e16736b <
    53141db979687eae7dc6d29414cefc77034f967e
  - >-
    Linux >= 81054476453640159149cb6704e834893e16736b <
    68891125af5a5dfbca728809a16637a869bbe0df
  - >-
    Linux >= 81054476453640159149cb6704e834893e16736b <
    b2d6d873b4dfb5b84194061c4b40a1cd85b92ca4
  - >-
    Linux >= 81054476453640159149cb6704e834893e16736b <
    77ea60f2d24002c308f224db44a4542c466489af
  - >-
    Linux >= 81054476453640159149cb6704e834893e16736b <
    25419f516ea84b1e7d3d55aae5215ac86ece0c66
  - >-
    Linux >= 81054476453640159149cb6704e834893e16736b <
    0ee697defc0594f1da810ed75d9d643fb46f5318
  - >-
    Linux >= 81054476453640159149cb6704e834893e16736b <
    2db9bfa3e27bdea15e05ea70b56bad3d21e570ec
  - Linux 4.11
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-16T19:22:22.091820Z'
published: '2026-09-11'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:47:26.175Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89477'
references:
  - url: 'https://git.kernel.org/stable/c/79ff751311e80fa0370007e46a79a6d601685e75'
  - url: 'https://git.kernel.org/stable/c/53141db979687eae7dc6d29414cefc77034f967e'
  - url: 'https://git.kernel.org/stable/c/68891125af5a5dfbca728809a16637a869bbe0df'
  - url: 'https://git.kernel.org/stable/c/b2d6d873b4dfb5b84194061c4b40a1cd85b92ca4'
  - url: 'https://git.kernel.org/stable/c/77ea60f2d24002c308f224db44a4542c466489af'
  - url: 'https://git.kernel.org/stable/c/25419f516ea84b1e7d3d55aae5215ac86ece0c66'
  - url: 'https://git.kernel.org/stable/c/0ee697defc0594f1da810ed75d9d643fb46f5318'
  - url: 'https://git.kernel.org/stable/c/2db9bfa3e27bdea15e05ea70b56bad3d21e570ec'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89477.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89477'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532238'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89477'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89477'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89477.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00501
epssPercentile: 0.42711
scores:
  cna: 7.5
  vendor: 7
ingestedAt: '2026-09-14T15:23:07.453Z'
---

## Overview

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.

## Affected

- `Linux >= 81054476453640159149cb6704e834893e16736b < 79ff751311e80fa0370007e46a79a6d601685e75`
- `Linux >= 81054476453640159149cb6704e834893e16736b < 53141db979687eae7dc6d29414cefc77034f967e`
- `Linux >= 81054476453640159149cb6704e834893e16736b < 68891125af5a5dfbca728809a16637a869bbe0df`
- `Linux >= 81054476453640159149cb6704e834893e16736b < b2d6d873b4dfb5b84194061c4b40a1cd85b92ca4`
- `Linux >= 81054476453640159149cb6704e834893e16736b < 77ea60f2d24002c308f224db44a4542c466489af`
- `Linux >= 81054476453640159149cb6704e834893e16736b < 25419f516ea84b1e7d3d55aae5215ac86ece0c66`
- `Linux >= 81054476453640159149cb6704e834893e16736b < 0ee697defc0594f1da810ed75d9d643fb46f5318`
- `Linux >= 81054476453640159149cb6704e834893e16736b < 2db9bfa3e27bdea15e05ea70b56bad3d21e570ec`
- `Linux 4.11`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-18 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89477.json)