---
id: CVE-2026-98276
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: lock the socket in sock_gettstamp()

  sk->sk_flags must only be changed while holding the socket lock,
  because sock_set_flag() and sock_reset_flag() use non atomic
  …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: lock the socket in sock_gettstamp()

  sk->sk_flags must only be changed while holding the socket lock,
  because sock_set_flag() and sock_reset_flag() use non atomic
  …
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    18899e2e4023369a8f7739c2255a59a9748d8d17
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    88c804847dd87dc613b771b392ccecdb94725032
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    3b12d3967e96f1b7b977d9fc352ae29a1b299a82
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    17b2a1eb97fdb2a2cbaeab3b146b26797ea9311f
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    1f73253add8365d0dad0a4f421acaa8c21d20cef
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    d9f96bc2d822501f84d1caa6275a2c6b316ca2c4
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    899650bbf985b7bfd2a7b808357df9b16e6d6959
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    9ed55f3dbef4f4adfe65eb03b0c35c53229a8490
  - Linux 2.6.12
published: '2026-10-06'
updated: '2026-10-06'
sourceUpdated: '2026-10-06T09:18:17.360'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-98276'
references:
  - url: 'https://git.kernel.org/stable/c/17b2a1eb97fdb2a2cbaeab3b146b26797ea9311f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/18899e2e4023369a8f7739c2255a59a9748d8d17'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/1f73253add8365d0dad0a4f421acaa8c21d20cef'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3b12d3967e96f1b7b977d9fc352ae29a1b299a82'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/88c804847dd87dc613b771b392ccecdb94725032'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/899650bbf985b7bfd2a7b808357df9b16e6d6959'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9ed55f3dbef4f4adfe65eb03b0c35c53229a8490'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d9f96bc2d822501f84d1caa6275a2c6b316ca2c4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-06T08:50:17.423Z'
---

## Overview

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

net: lock the socket in sock_gettstamp()

sk->sk_flags must only be changed while holding the socket lock,
because sock_set_flag() and sock_reset_flag() use non atomic
operations (__set_bit() and __clear_bit()).

sock_gettstamp() is one of the last places where a bit of sk->sk_flags
is changed from a syscall without owning the socket lock, through
sock_enable_timestamp(sk, SOCK_TIMESTAMP).

sk_set_memalloc() and sk_clear_memalloc() also change sk->sk_flags
without the socket lock, but their callers (nbd, iscsi_tcp, nvme-tcp,
sunrpc, wireguard) need a careful audit, this will be addressed in a
separate patch.

Jungwoo Lee and Wongi Lee reported an UDP socket use-after-free
caused by this bug: a SIOCGSTAMPNS_NEW ioctl racing with bind()
can cancel the SOCK_RCU_FREE bit that udp_lib_get_port() just set,
because both threads perform a read-modify-write on the same word.

  CPU 0 (bind)                        CPU 1 (SIOCGSTAMPNS_NEW)
  --------------------------------    ----------------------------
  read sk_flags = F                   read sk_flags = F
  compute F | BIT(SOCK_RCU_FREE)      compute F | BIT(SOCK_TIMESTAMP)
  store F | BIT(SOCK_RCU_FREE)
  sk_add_node_rcu(sk, ...)
                                      store F | BIT(SOCK_TIMESTAMP)

After the lost update, SOCK_RCU_FREE is clear while the socket is
visible to lockless UDP receive lookups. sk_destruct() then frees
the socket immediately instead of waiting for a RCU grace period,
while the receive path still holds a reference-less pointer to it:

 BUG: KASAN: slab-use-after-free in ipv4_pktinfo_prepare+0x30/0x410
 Read of size 8 at addr ffff888008806610 by task exploit/207
 CPU: 0 UID: 1000 PID: 207 Comm: exploit Not tainted 6.12.95+ #1
  ipv4_pktinfo_prepare+0x30/0x410
  udp_queue_rcv_one_skb+0x51c/0x1180
  udp_unicast_rcv_skb+0x109/0x350
  ip_protocol_deliver_rcu+0x14b/0x310
  ip_local_deliver_finish+0x29d/0x390
  ip_local_deliver+0x24d/0x2a0

Only grab the socket lock when SOCK_TIMESTAMP has to be set,
to keep the common case lockless.

## Remediation

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