---
id: CVE-2026-23243
title: 'RDMA/umad: Reject negative data_len in ib_umad_write'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  RDMA/umad: Reject negative data_len in ib_umad_write

  ib_umad_write computes data_len from user-controlled count and the
  MAD header sizes. With a mismatched user MAD he…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a <
    1371ef6b1ecf3676b8942f5dfb3634fb0648128e
  - >-
    Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a <
    362e45fd9069ffa1523f9f1633b606ebf72060d7
  - >-
    Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a <
    6eb2919474ca105c5b13d19574e25f0ddcf19ca2
  - >-
    Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a <
    a6a3e4af10993cb9e4b8f0548680aba0ab5f3b0d
  - >-
    Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a <
    9c80d688f402539dfc8f336de1380d6b4ee14316
  - >-
    Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a <
    205955f29c26330b1dc7fdeadd5bb97c38e26f56
  - >-
    Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a <
    52ab82cc5cf8ada5c3fb6ffe8f32fdb2fc27a34b
  - >-
    Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a <
    5551b02fdbfd85a325bb857f3a8f9c9f33397ed2
  - Linux 2.6.24
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-06-17T17:47:24.163717Z'
published: '2026-03-18'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T08:45:08.401Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-23243'
references:
  - url: 'https://git.kernel.org/stable/c/1371ef6b1ecf3676b8942f5dfb3634fb0648128e'
  - url: 'https://git.kernel.org/stable/c/362e45fd9069ffa1523f9f1633b606ebf72060d7'
  - url: 'https://git.kernel.org/stable/c/6eb2919474ca105c5b13d19574e25f0ddcf19ca2'
  - url: 'https://git.kernel.org/stable/c/a6a3e4af10993cb9e4b8f0548680aba0ab5f3b0d'
  - url: 'https://git.kernel.org/stable/c/9c80d688f402539dfc8f336de1380d6b4ee14316'
  - url: 'https://git.kernel.org/stable/c/205955f29c26330b1dc7fdeadd5bb97c38e26f56'
  - url: 'https://git.kernel.org/stable/c/52ab82cc5cf8ada5c3fb6ffe8f32fdb2fc27a34b'
  - url: 'https://git.kernel.org/stable/c/5551b02fdbfd85a325bb857f3a8f9c9f33397ed2'
tags:
  - cve.org
epss: 0.00131
epssPercentile: 0.03038
ingestedAt: '2026-09-08T15:33:26.993Z'
---

## Overview

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

RDMA/umad: Reject negative data_len in ib_umad_write

ib_umad_write computes data_len from user-controlled count and the
MAD header sizes. With a mismatched user MAD header size and RMPP
header length, data_len can become negative and reach ib_create_send_mad().
This can make the padding calculation exceed the segment size and trigger
an out-of-bounds memset in alloc_send_rmpp_list().

Add an explicit check to reject negative data_len before creating the
send buffer.

KASAN splat:
[  211.363464] BUG: KASAN: slab-out-of-bounds in ib_create_send_mad+0xa01/0x11b0
[  211.364077] Write of size 220 at addr ffff88800c3fa1f8 by task spray_thread/102
[  211.365867] ib_create_send_mad+0xa01/0x11b0
[  211.365887] ib_umad_write+0x853/0x1c80

## Affected

- `Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a < 1371ef6b1ecf3676b8942f5dfb3634fb0648128e`
- `Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a < 362e45fd9069ffa1523f9f1633b606ebf72060d7`
- `Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a < 6eb2919474ca105c5b13d19574e25f0ddcf19ca2`
- `Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a < a6a3e4af10993cb9e4b8f0548680aba0ab5f3b0d`
- `Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a < 9c80d688f402539dfc8f336de1380d6b4ee14316`
- `Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a < 205955f29c26330b1dc7fdeadd5bb97c38e26f56`
- `Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a < 52ab82cc5cf8ada5c3fb6ffe8f32fdb2fc27a34b`
- `Linux >= 2be8e3ee8efd6f99ce454115c29d09750915021a < 5551b02fdbfd85a325bb857f3a8f9c9f33397ed2`
- `Linux 2.6.24`

## Remediation

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