---
id: CVE-2026-97566
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  mptcp: pm: kernel: drop pending ADD_ADDR when removing ID0

  The in-kernel MPTCP path manager can leave a stale ADD_ADDR announcement
  entry alive when removing the id 0 …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  mptcp: pm: kernel: drop pending ADD_ADDR when removing ID0

  The in-kernel MPTCP path manager can leave a stale ADD_ADDR announcement
  entry alive when removing the id 0 …
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-617
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 740d798e8767d8a449902b1a1bbc70facfce19b5 <
    bacf23e7c9876c9f4170166b3597cb22ea3ed39b
  - >-
    Linux >= 740d798e8767d8a449902b1a1bbc70facfce19b5 <
    d4a67a880654e1bfe318a31bea0bdbb026a09ade
  - >-
    Linux >= 740d798e8767d8a449902b1a1bbc70facfce19b5 <
    545616b4e7325be3c61fc082538cb06d14f7b1db
  - >-
    Linux >= 740d798e8767d8a449902b1a1bbc70facfce19b5 <
    2ac7d6e620764f1fc79eb4edd3610a7a661981ca
  - Linux 5.13
published: '2026-09-25'
updated: '2026-10-03'
sourceUpdated: '2026-10-03T11:18:04.090'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-97566'
references:
  - url: 'https://git.kernel.org/stable/c/2ac7d6e620764f1fc79eb4edd3610a7a661981ca'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/545616b4e7325be3c61fc082538cb06d14f7b1db'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/bacf23e7c9876c9f4170166b3597cb22ea3ed39b'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d4a67a880654e1bfe318a31bea0bdbb026a09ade'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97566.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-97566'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2541203'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-97566'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-97566'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-97566.mbox
  - url: 'https://git.kernel.org/stable/c/189d60057e5f3d6a62e3d71a3cc428c9150bc14f'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00206
epssPercentile: 0.10584
cvssSource: vendor
ingestedAt: '2026-09-25T11:06:38.914Z'
---

## Overview

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

mptcp: pm: kernel: drop pending ADD_ADDR when removing ID0

The in-kernel MPTCP path manager can leave a stale ADD_ADDR announcement
entry alive when removing the id 0 endpoint. This happens because the id 0
removal path does not tear down pending announcements, unlike the non-zero
id path.

When the PM later reselects id 0 after adding another signal endpoint, it
finds the stale anno_list entry and hits WARN_ON_ONCE(mptcp_pm_is_kernel())
in mptcp_pm_announced_alloc().

Root cause: asymmetry between removal paths.
- Non-zero id path: mptcp_nl_remove_subflow_and_signal_addr() calls
  mptcp_pm_remove_announced() to clean up.
- Id 0 path: mptcp_nl_remove_id_zero_address() skips cleanup entirely.

Fix by making the id 0 path symmetric: call mptcp_pm_announced_remove()
and decrement add_addr_signaled before queuing the RM_ADDR.

Subtle detail: signal endpoints are stored in anno_list with port 0, but
msk_local carries the connection's local port. In other words, entries
linked to ID0 paths should have port == 0. A follow-up patch will ensure
that. mptcp_pm_announced_remove() uses use_port=true for comparison. So
clear the port before the lookup.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Low · affected: Red Hat Enterprise Linux 10 · no fix planned: Red Hat Enterprise Linux 10 · updated 2026-10-17 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-97566.json)