---
id: CVE-2026-45856
title: 'RDMA/uverbs: Validate wqe_size before using it in ib_uverbs_post_send'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  RDMA/uverbs: Validate wqe_size before using it in ib_uverbs_post_send

  ib_uverbs_post_send() uses cmd.wqe_size from userspace without any
  validation before passing it t…
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= c3bea3d2dc5358e05541527283279102383b0231 <
    9c15ec4cd4e7f57c6bbcb4e73e99290f150dd2a7
  - >-
    Linux >= c3bea3d2dc5358e05541527283279102383b0231 <
    9b5ac1c15334d46c0dbd49d64a2257b929500163
  - >-
    Linux >= c3bea3d2dc5358e05541527283279102383b0231 <
    01c9b152647dc70dc06a4a2eff86ebb3b3c76075
  - >-
    Linux >= c3bea3d2dc5358e05541527283279102383b0231 <
    bf1feed1a7886af945f92890493aefd2b5c9928a
  - >-
    Linux >= c3bea3d2dc5358e05541527283279102383b0231 <
    d533425ac1f2925b4fc3e4ed9b9d72362cb23475
  - >-
    Linux >= c3bea3d2dc5358e05541527283279102383b0231 <
    bf4454da8b1e712714628c0a0d6e7845bb40790a
  - >-
    Linux >= c3bea3d2dc5358e05541527283279102383b0231 <
    bef70ff9841990658610512b4a18e4a88c9b4df6
  - >-
    Linux >= c3bea3d2dc5358e05541527283279102383b0231 <
    1956f0a74ccf5dc9c3ef717f2985c3ed3400aab0
  - Linux 5.0
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-16T15:18:02.441726Z'
published: '2026-05-27'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:20:44.029Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-45856'
references:
  - url: 'https://git.kernel.org/stable/c/9c15ec4cd4e7f57c6bbcb4e73e99290f150dd2a7'
  - url: 'https://git.kernel.org/stable/c/9b5ac1c15334d46c0dbd49d64a2257b929500163'
  - url: 'https://git.kernel.org/stable/c/01c9b152647dc70dc06a4a2eff86ebb3b3c76075'
  - url: 'https://git.kernel.org/stable/c/bf1feed1a7886af945f92890493aefd2b5c9928a'
  - url: 'https://git.kernel.org/stable/c/d533425ac1f2925b4fc3e4ed9b9d72362cb23475'
  - url: 'https://git.kernel.org/stable/c/bf4454da8b1e712714628c0a0d6e7845bb40790a'
  - url: 'https://git.kernel.org/stable/c/bef70ff9841990658610512b4a18e4a88c9b4df6'
  - url: 'https://git.kernel.org/stable/c/1956f0a74ccf5dc9c3ef717f2985c3ed3400aab0'
tags:
  - cve.org
epss: 0.00165
epssPercentile: 0.05306
ingestedAt: '2026-10-16T17:24:46.699Z'
---

## Overview

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

RDMA/uverbs: Validate wqe_size before using it in ib_uverbs_post_send

ib_uverbs_post_send() uses cmd.wqe_size from userspace without any
validation before passing it to kmalloc() and using the allocated
buffer as struct ib_uverbs_send_wr.

If a user provides a small wqe_size value (e.g., 1), kmalloc() will
succeed, but subsequent accesses to user_wr->opcode, user_wr->num_sge,
and other fields will read beyond the allocated buffer, resulting in
an out-of-bounds read from kernel heap memory. This could potentially
leak sensitive kernel information to userspace.

Additionally, providing an excessively large wqe_size can trigger a
WARNING in the memory allocation path, as reported by syzkaller.

This is inconsistent with ib_uverbs_unmarshall_recv() which properly
validates that wqe_size >= sizeof(struct ib_uverbs_recv_wr) before
proceeding.

Add the same validation for ib_uverbs_post_send() to ensure wqe_size
is at least sizeof(struct ib_uverbs_send_wr).

## Affected

- `Linux >= c3bea3d2dc5358e05541527283279102383b0231 < 9c15ec4cd4e7f57c6bbcb4e73e99290f150dd2a7`
- `Linux >= c3bea3d2dc5358e05541527283279102383b0231 < 9b5ac1c15334d46c0dbd49d64a2257b929500163`
- `Linux >= c3bea3d2dc5358e05541527283279102383b0231 < 01c9b152647dc70dc06a4a2eff86ebb3b3c76075`
- `Linux >= c3bea3d2dc5358e05541527283279102383b0231 < bf1feed1a7886af945f92890493aefd2b5c9928a`
- `Linux >= c3bea3d2dc5358e05541527283279102383b0231 < d533425ac1f2925b4fc3e4ed9b9d72362cb23475`
- `Linux >= c3bea3d2dc5358e05541527283279102383b0231 < bf4454da8b1e712714628c0a0d6e7845bb40790a`
- `Linux >= c3bea3d2dc5358e05541527283279102383b0231 < bef70ff9841990658610512b4a18e4a88c9b4df6`
- `Linux >= c3bea3d2dc5358e05541527283279102383b0231 < 1956f0a74ccf5dc9c3ef717f2985c3ed3400aab0`
- `Linux 5.0`

## Remediation

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