---
id: CVE-2026-53175
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  inet: frags: fix use-after-free caused by the fqdir_pre_exit() flush

  On netns teardown, fqdir_pre_exit() walks the fqdir rhashtable and
  flushes every fragment queue th…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  inet: frags: fix use-after-free caused by the fqdir_pre_exit() flush

  On netns teardown, fqdir_pre_exit() walks the fqdir rhashtable and
  flushes every fragment queue th…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-416
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 6.18.3, < 6.18.36'
  - 'linux_kernel >= 6.19.1, < 7.0.13'
  - linux_kernel = 6.12.93
  - linux_kernel = 6.19
  - linux_kernel = 7.1
patched:
  - linux_kernel 7.0.13
published: '2026-06-25'
updated: '2026-07-06'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-53175'
references:
  - url: 'https://git.kernel.org/stable/c/010c3313a4d178dc2d3ce958d2e5cb055e2864c1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/0e823ca0e7391630784ae7dd0981b7ad170a93d9'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/32594b09854970d7ba83eb2dc8c69a2edd158c8e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/89b909e9704587bfecc1aab1d37e98faee03b9f9'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c22599cc90e1cd5f8129c8670bd68a02ff7177b4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://access.redhat.com/security/cve/CVE-2026-53175'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2492840'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-53175.json
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
tags:
  - nvd
epss: 0.0045
epssPercentile: 0.36351
ingestedAt: '2026-07-06T17:44:51.375Z'
---

## Overview

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

inet: frags: fix use-after-free caused by the fqdir_pre_exit() flush

On netns teardown, fqdir_pre_exit() walks the fqdir rhashtable and
flushes every fragment queue that is not yet complete using
inet_frag_queue_flush(). That helper frees all the skbs queued on the
fragment queue but does not set INET_FRAG_COMPLETE, and leaves
q->fragments_tail and q->last_run_head pointing at the freed skbs.
The queue itself stays in the rhashtable.

fqdir_pre_exit() first lowers high_thresh to 0 to stop new queue lookups,
but it cannot stop a fragment that already obtained the queue through
inet_frag_find() earlier and stalled just before taking the queue lock.
Once that fragment resumes after the flush and takes the queue lock,
it passes the INET_FRAG_COMPLETE check and then dereferences the freed
fragments_tail. inet_frag_queue_insert() reads FRAG_CB() and ->len of
that pointer and, on the append path, writes ->next_frag, causing a
slab use-after-free. IPv6, nf_conntrack_reasm6 and 6lowpan reassembly
share the same flush path and are affected as well.

Reset rb_fragments, fragments_tail and last_run_head in
inet_frag_queue_flush() so a flushed queue no longer points at the
freed skbs. A fragment that resumes after the flush and takes the
queue lock then finds an empty queue and starts a new run instead of
dereferencing the freed fragments_tail. ip_frag_reinit() already
performed this reset after its own flush, so drop the now duplicate
code there.

## Affected

- `linux_kernel >= 6.18.3, < 6.18.36`
- `linux_kernel >= 6.19.1, < 7.0.13`
- `linux_kernel = 6.12.93`
- `linux_kernel = 6.19`
- `linux_kernel = 7.1`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.0.13`