---
id: CVE-2026-98550
title: >-
  kernel: tipc: reject invalid and unexpected GRP_ACK_MSG to prevent bc_ackers
  underflow (CVE-2026-98550)
summary: >-
  A flaw was found in the TIPC (Transparent Inter-Process Communication)
  subsystem of the Linux kernel. This flaw allows an attacker to cause a Denial
  of Service (DoS) by sending unexpected or duplicate group acknowledgment
  messages. Due to …
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: vendor
cwe: CWE-191
vendor: Red Hat
product: Red Hat Enterprise Linux 9
affected:
  - enterprise_linux 10
  - enterprise_linux 8
  - enterprise_linux 9
  - openshift_container_platform 4
published: '2026-10-18'
updated: '2026-10-24'
sourceUpdated: '2026-10-24T14:22:57+00:00'
source: CSAF
sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98550.json'
references:
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98550.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-98550'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2554946'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-98550'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-98550'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98550.mbox
  - url: 'https://git.kernel.org/stable/c/edc6593c442278fceff0120e8cc58bc592168c35'
  - url: 'https://git.kernel.org/stable/c/9b94a90651e1fa573c6ac6a5a6b269d5874df2c0'
  - url: 'https://git.kernel.org/stable/c/507a27435b2bb1f22e3a3674f6a6553eb815021b'
  - url: 'https://git.kernel.org/stable/c/80a9ccfc24d3776ef6753a57315e726475fac7d7'
  - url: 'https://git.kernel.org/stable/c/478fb08d0c2a53002a721d22b8d6681ec971d90f'
  - url: 'https://git.kernel.org/stable/c/12cc3a1eac5a2a06b67a7b85f0f48ff241a94d1b'
  - url: 'https://git.kernel.org/stable/c/b0e517961f09b9f60d338d1ea4e17aacdbf206f0'
  - url: 'https://git.kernel.org/stable/c/99cc2a62e07a44a22254d7beca9ef1f8ad886d0d'
tags:
  - csaf
  - vex
  - red-hat
  - cve.org
epss: 0.00677
epssPercentile: 0.52095
ingestedAt: '2026-10-18T15:45:12.264Z'
---

## Overview

A flaw was found in the TIPC (Transparent Inter-Process Communication) subsystem of the Linux kernel. This flaw allows an attacker to cause a Denial of Service (DoS) by sending unexpected or duplicate group acknowledgment messages. Due to improper validation of incoming protocol messages, an internal acknowledgment counter can underflow, permanently placing the socket into a congested state and blocking all subsequent broadcast communication.

## Vendor advisories

- **Red Hat VEX** · Important · 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 2026-10-24 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98550.json)

**kernel: tipc: reject invalid and unexpected GRP_ACK_MSG to prevent bc_ackers underflow** — rated Important by Red Hat. Released 2026-10-18, updated 2026-10-24.

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

Not affected:

- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7

## Remediation

Affected

Workarounds / mitigations:

- --- CME Mitigation Guidance (2026-10-20) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.

The highest-value action is to enforce strict sequence verification and reject unexpected GRP_ACK_MSG messages in…