---
id: CVE-2025-21868
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: allow small head cache usage with large MAX_SKB_FRAGS values

  Sabrina reported the following splat:

      WARNING: CPU: 0 PID: 1 at net/core/dev.c:6935 netif_napi_a…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: allow small head cache usage with large MAX_SKB_FRAGS values

  Sabrina reported the following splat:

      WARNING: CPU: 0 PID: 1 at net/core/dev.c:6935 netif_napi_a…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 6.4, < 6.12.17'
  - 'linux_kernel >= 6.13, < 6.13.5'
  - linux_kernel = 6.14
patched:
  - linux_kernel 6.13.5
published: '2025-03-27'
updated: '2026-07-30'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-21868'
references:
  - url: 'https://git.kernel.org/stable/c/14ad6ed30a10afbe91b0749d6378285f4225d482'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/648e440c98e260dec835e48a5d7a9993477b1f9d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ed0ca7d2127c63991cfaf1932b827e3f4f8ee480'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ed8a77fee4618facd2a539cad7b7366697b5a575'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21868.json
  - url: 'https://access.redhat.com/security/cve/CVE-2025-21868'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2355331'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2025-21868'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2025-21868'
  - url: >-
      https://lore.kernel.org/linux-cve-announce/2025032734-CVE-2025-21868-ef4f@gregkh/T
tags:
  - nvd
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.00375
epssPercentile: 0.287
ingestedAt: '2026-07-30T06:53:10.595Z'
cwe:
  - CWE-787
scores:
  nvd: 7.5
  vendor: 3.3
---

## Overview

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

net: allow small head cache usage with large MAX_SKB_FRAGS values

Sabrina reported the following splat:

    WARNING: CPU: 0 PID: 1 at net/core/dev.c:6935 netif_napi_add_weight_locked+0x8f2/0xba0
    Modules linked in:
    CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.14.0-rc1-net-00092-g011b03359038 #996
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014
    RIP: 0010:netif_napi_add_weight_locked+0x8f2/0xba0
    Code: e8 c3 e6 6a fe 48 83 c4 28 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc c7 44 24 10 ff ff ff ff e9 8f fb ff ff e8 9e e6 6a fe <0f> 0b e9 d3 fe ff ff e8 92 e6 6a fe 48 8b 04 24 be ff ff ff ff 48
    RSP: 0000:ffffc9000001fc60 EFLAGS: 00010293
    RAX: 0000000000000000 RBX: ffff88806ce48128 RCX: 1ffff11001664b9e
    RDX: ffff888008f00040 RSI: ffffffff8317ca42 RDI: ffff88800b325cb6
    RBP: ffff88800b325c40 R08: 0000000000000001 R09: ffffed100167502c
    R10: ffff88800b3a8163 R11: 0000000000000000 R12: ffff88800ac1c168
    R13: ffff88800ac1c168 R14: ffff88800ac1c168 R15: 0000000000000007
    FS:  0000000000000000(0000) GS:ffff88806ce00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: ffff888008201000 CR3: 0000000004c94001 CR4: 0000000000370ef0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
    <TASK>
    gro_cells_init+0x1ba/0x270
    xfrm_input_init+0x4b/0x2a0
    xfrm_init+0x38/0x50
    ip_rt_init+0x2d7/0x350
    ip_init+0xf/0x20
    inet_init+0x406/0x590
    do_one_initcall+0x9d/0x2e0
    do_initcalls+0x23b/0x280
    kernel_init_freeable+0x445/0x490
    kernel_init+0x20/0x1d0
    ret_from_fork+0x46/0x80
    ret_from_fork_asm+0x1a/0x30
    </TASK>
    irq event stamp: 584330
    hardirqs last  enabled at (584338): [<ffffffff8168bf87>] __up_console_sem+0x77/0xb0
    hardirqs last disabled at (584345): [<ffffffff8168bf6c>] __up_console_sem+0x5c/0xb0
    softirqs last  enabled at (583242): [<ffffffff833ee96d>] netlink_insert+0x14d/0x470
    softirqs last disabled at (583754): [<ffffffff8317c8cd>] netif_napi_add_weight_locked+0x77d/0xba0

on kernel built with MAX_SKB_FRAGS=45, where SKB_WITH_OVERHEAD(1024)
is smaller than GRO_MAX_HEAD.

Such built additionally contains the revert of the single page frag cache
so that napi_get_frags() ends up using the page frag allocator, triggering
the splat.

Note that the underlying issue is independent from the mentioned
revert; address it ensuring that the small head cache will fit either TCP
and GRO allocation and updating napi_alloc_skb() and __netdev_alloc_skb()
to select kmalloc() usage for any allocation fitting such cache.

## Affected

- `linux_kernel >= 6.4, < 6.12.17`
- `linux_kernel >= 6.13, < 6.13.5`
- `linux_kernel = 6.14`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.13.5`

## Vendor advisories

- **Red Hat VEX** · Low · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 10 · updated 2026-09-13 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21868.json)