---
id: CVE-2026-89476
title: 'sctp: fix stream->outcnt underflow on duplicate RECONF responses'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  sctp: fix stream->outcnt underflow on duplicate RECONF responses

  A cached RECONF chunk may contain more than one request parameter.  A
  duplicate response can therefore…
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-191
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 <
    041f7df5a929d3e7435dd8387e8ea17f2d412b7d
  - >-
    Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 <
    59f61c39cb99ee1737bd742a20094fe5653389bb
  - >-
    Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 <
    793519e343867ee9a3e84f6cac07f81f2aec7b5d
  - >-
    Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 <
    092acd3c55a4077b00489064615d8d2d898daf91
  - >-
    Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 <
    2d867663c563e8009257b9edf9c8ec75d9bbf19a
  - >-
    Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 <
    d02a5794c3deedcb8476d017fcee2b7aaedab2e1
  - >-
    Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 <
    8320cbd81bc21a1ca6ebdf70ad610ebc5ef1bd68
  - >-
    Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 <
    3faf13aff243ca9f78d08b1a2956ef5a6fc77b6e
  - Linux 4.12
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-16T19:22:19.523303Z'
published: '2026-09-11'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:47:25.179Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89476'
references:
  - url: 'https://git.kernel.org/stable/c/041f7df5a929d3e7435dd8387e8ea17f2d412b7d'
  - url: 'https://git.kernel.org/stable/c/59f61c39cb99ee1737bd742a20094fe5653389bb'
  - url: 'https://git.kernel.org/stable/c/793519e343867ee9a3e84f6cac07f81f2aec7b5d'
  - url: 'https://git.kernel.org/stable/c/092acd3c55a4077b00489064615d8d2d898daf91'
  - url: 'https://git.kernel.org/stable/c/2d867663c563e8009257b9edf9c8ec75d9bbf19a'
  - url: 'https://git.kernel.org/stable/c/d02a5794c3deedcb8476d017fcee2b7aaedab2e1'
  - url: 'https://git.kernel.org/stable/c/8320cbd81bc21a1ca6ebdf70ad610ebc5ef1bd68'
  - url: 'https://git.kernel.org/stable/c/3faf13aff243ca9f78d08b1a2956ef5a6fc77b6e'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89476.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89476'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532035'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89476'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89476'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89476.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00696
epssPercentile: 0.52818
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 stream->outcnt underflow on duplicate RECONF responses

A cached RECONF chunk may contain more than one request parameter.  A
duplicate response can therefore find and process the same ADD_OUT request
again while another parameter is still outstanding, rolling back outcnt
twice and possibly underflowing it.

Track outstanding request types as bits and clear each bit after its first
response.  Later responses for the same request are then ignored.

## Affected

- `Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 < 041f7df5a929d3e7435dd8387e8ea17f2d412b7d`
- `Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 < 59f61c39cb99ee1737bd742a20094fe5653389bb`
- `Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 < 793519e343867ee9a3e84f6cac07f81f2aec7b5d`
- `Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 < 092acd3c55a4077b00489064615d8d2d898daf91`
- `Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 < 2d867663c563e8009257b9edf9c8ec75d9bbf19a`
- `Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 < d02a5794c3deedcb8476d017fcee2b7aaedab2e1`
- `Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 < 8320cbd81bc21a1ca6ebdf70ad610ebc5ef1bd68`
- `Linux >= 11ae76e67a179f25ae8f772d62a7ddf717b1cdf3 < 3faf13aff243ca9f78d08b1a2956ef5a6fc77b6e`
- `Linux 4.12`

## 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 2026-09-14 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89476.json)