---
id: CVE-2026-68386
title: 'bpf, sockmap: Reject unhashed UDP sockets on sockmap update'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bpf, sockmap: Reject unhashed UDP sockets on sockmap update

  UDP sockets get SOCK_RCU_FREE set when (auto-)bound. This means
  sk_is_refcounted(unbound) = true, while sk_…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b <
    2271276ac5279d2d204be7739a1a28d4ef6cf608
  - >-
    Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b <
    7ffe529e7127411806c8692fb1490f552c629dc2
  - >-
    Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b <
    17b7ef6b86112a4e61cee1e9009a4b318e3225c5
  - >-
    Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b <
    250474c69bc3fc48a5fc21d7c349f279caad947a
  - >-
    Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b <
    8692655da369961128658cf8539334b6a960ecb0
  - >-
    Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b <
    66efd3368ae10d05e08fbe6425b50fdec7186ac7
  - Linux 5.15
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T16:48:28.442498Z'
published: '2026-08-10'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T16:55:15.101Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-68386'
references:
  - url: 'https://git.kernel.org/stable/c/2271276ac5279d2d204be7739a1a28d4ef6cf608'
  - url: 'https://git.kernel.org/stable/c/7ffe529e7127411806c8692fb1490f552c629dc2'
  - url: 'https://git.kernel.org/stable/c/17b7ef6b86112a4e61cee1e9009a4b318e3225c5'
  - url: 'https://git.kernel.org/stable/c/250474c69bc3fc48a5fc21d7c349f279caad947a'
  - url: 'https://git.kernel.org/stable/c/8692655da369961128658cf8539334b6a960ecb0'
  - url: 'https://git.kernel.org/stable/c/66efd3368ae10d05e08fbe6425b50fdec7186ac7'
tags:
  - cve.org
epss: 0.00211
epssPercentile: 0.11442
ingestedAt: '2026-11-06T18:00:12.606Z'
---

## Overview

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

bpf, sockmap: Reject unhashed UDP sockets on sockmap update

UDP sockets get SOCK_RCU_FREE set when (auto-)bound. This means
sk_is_refcounted(unbound) = true, while sk_is_refcounted(bound) = false.

Because sockmap accepts unbound UDP sockets, a BPF program can increment a
socket's refcount via lookup. If the socket is subsequently bound, the
transition from unbound to bound causes bpf_sk_release() to skip the
decrement of the refcount, causing a memory leak.

unreferenced object 0xffff88810bc2eb40 (size 1984):
  comm "test_progs", pid 2451, jiffies 4295320596
  hex dump (first 32 bytes):
    7f 00 00 01 7f 00 00 01 d2 04 1b b7 04 d2 00 00  ................
    02 00 01 40 00 00 00 00 00 00 00 00 00 00 00 00  ...@............
  backtrace (crc bdee079d):
    kmem_cache_alloc_noprof+0x557/0x660
    sk_prot_alloc+0x69/0x240
    sk_alloc+0x30/0x460
    inet_create+0x2ce/0xf80
    __sock_create+0x25b/0x5c0
    __sys_socket+0x119/0x1d0
    __x64_sys_socket+0x72/0xd0
    do_syscall_64+0xa1/0x5f0
    entry_SYSCALL_64_after_hwframe+0x76/0x7e

Instead of special-casing for refcounted sockets, reject unhashed UDP
sockets during sockmap updates, as there is no benefit to supporting those.
This effectively reverts the commit under Fixes, with two exceptions:

1. sock_map_sk_state_allowed() maintains a fall-through `return true`.
2. In the spirit of commit b8b8315e39ff ("bpf, sockmap: Remove unhash
   handler for BPF sockmap usage"), the proto::unhash BPF handler is not
   reintroduced.

Historical note: this issue is related to commit 67312adc96b5 ("bpf: reject
unhashed sockets in bpf_sk_assign").

## Affected

- `Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b < 2271276ac5279d2d204be7739a1a28d4ef6cf608`
- `Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b < 7ffe529e7127411806c8692fb1490f552c629dc2`
- `Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b < 17b7ef6b86112a4e61cee1e9009a4b318e3225c5`
- `Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b < 250474c69bc3fc48a5fc21d7c349f279caad947a`
- `Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b < 8692655da369961128658cf8539334b6a960ecb0`
- `Linux >= 0c48eefae712c2fd91480346a07a1a9cd0f9470b < 66efd3368ae10d05e08fbe6425b50fdec7186ac7`
- `Linux 5.15`

## Remediation

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