---
id: CVE-2025-21683
title: 'bpf: Fix bpf_sk_select_reuseport() memory leak'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf: Fix bpf_sk_select_reuseport() memory leak

  As pointed out in the original comment, lookup in sockmap can return a TCP
  ESTABLISHED socket. Such TCP socket may have …
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'
cvssSource: adp
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df <
    bb36838dac7bb334a3f3d7eb29875593ec9473fc
  - >-
    Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df <
    0ab52a8ca6e156a64c51b5e7456cac9a0ebfd9bf
  - >-
    Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df <
    d0a3b3d1176d39218b8edb2a2d03164942ab9ccd
  - >-
    Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df <
    b02e70be498b138e9c21701c2f33f4018ca7cd5e
  - >-
    Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df <
    cccd51dd22574216e64e5d205489e634f86999f3
  - >-
    Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df <
    b3af60928ab9129befa65e6df0310d27300942bf
  - Linux 5.8
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2025-10-01T19:51:47.465503Z'
published: '2025-01-31'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T01:03:01.511Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-21683'
references:
  - url: 'https://git.kernel.org/stable/c/bb36838dac7bb334a3f3d7eb29875593ec9473fc'
  - url: 'https://git.kernel.org/stable/c/0ab52a8ca6e156a64c51b5e7456cac9a0ebfd9bf'
  - url: 'https://git.kernel.org/stable/c/d0a3b3d1176d39218b8edb2a2d03164942ab9ccd'
  - url: 'https://git.kernel.org/stable/c/b02e70be498b138e9c21701c2f33f4018ca7cd5e'
  - url: 'https://git.kernel.org/stable/c/cccd51dd22574216e64e5d205489e634f86999f3'
  - url: 'https://git.kernel.org/stable/c/b3af60928ab9129befa65e6df0310d27300942bf'
tags:
  - cve.org
epss: 0.00224
epssPercentile: 0.12919
ingestedAt: '2026-10-15T04:46:37.355Z'
---

## Overview

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

bpf: Fix bpf_sk_select_reuseport() memory leak

As pointed out in the original comment, lookup in sockmap can return a TCP
ESTABLISHED socket. Such TCP socket may have had SO_ATTACH_REUSEPORT_EBPF
set before it was ESTABLISHED. In other words, a non-NULL sk_reuseport_cb
does not imply a non-refcounted socket.

Drop sk's reference in both error paths.

unreferenced object 0xffff888101911800 (size 2048):
  comm "test_progs", pid 44109, jiffies 4297131437
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    80 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc 9336483b):
    __kmalloc_noprof+0x3bf/0x560
    __reuseport_alloc+0x1d/0x40
    reuseport_alloc+0xca/0x150
    reuseport_attach_prog+0x87/0x140
    sk_reuseport_attach_bpf+0xc8/0x100
    sk_setsockopt+0x1181/0x1990
    do_sock_setsockopt+0x12b/0x160
    __sys_setsockopt+0x7b/0xc0
    __x64_sys_setsockopt+0x1b/0x30
    do_syscall_64+0x93/0x180
    entry_SYSCALL_64_after_hwframe+0x76/0x7e

## Affected

- `Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df < bb36838dac7bb334a3f3d7eb29875593ec9473fc`
- `Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df < 0ab52a8ca6e156a64c51b5e7456cac9a0ebfd9bf`
- `Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df < d0a3b3d1176d39218b8edb2a2d03164942ab9ccd`
- `Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df < b02e70be498b138e9c21701c2f33f4018ca7cd5e`
- `Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df < cccd51dd22574216e64e5d205489e634f86999f3`
- `Linux >= 64d85290d79c0677edb5a8ee2295b36c022fa5df < b3af60928ab9129befa65e6df0310d27300942bf`
- `Linux 5.8`

## Remediation

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