---
id: CVE-2026-64269
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  RDMA/rtrs-srv: Bound RDMA-Write length to chunk size in rdma_write_sg

  When the server answers an RTRS READ, rdma_write_sg() builds the source
  scatter/gather entry for …
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  RDMA/rtrs-srv: Bound RDMA-Write length to chunk size in rdma_write_sg

  When the server answers an RTRS READ, rdma_write_sg() builds the source
  scatter/gather entry for …
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H'
published: '2026-07-25'
updated: '2026-07-27'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-64269'
references:
  - url: 'https://git.kernel.org/stable/c/2912f3d40355dabc08fdbaaf2764d02445fe88dc'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/5a45d0aa1fa50a333ce5763ade744e2d89838667'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/68c09762172f6224e9ddf9b0a60bacbb36e443eb'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6cada540150894e81042a0ae0c796a21a9a877da'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6f40246f4312fdbab5a13cc440adebf95eb2aa66'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/963af8d97a8c6a117134a8d0db1415e0489200b1'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/da3e44add94b05dfde56f898421922f5cf35705f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00714
epssPercentile: 0.51672
ingestedAt: '2026-07-27T06:16:49.749Z'
---

## Overview

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

RDMA/rtrs-srv: Bound RDMA-Write length to chunk size in rdma_write_sg

When the server answers an RTRS READ, rdma_write_sg() builds the source
scatter/gather entry for the IB_WR_RDMA_WRITE that returns data to the
peer. Its length is taken directly from the wire descriptor:

  plist->length = le32_to_cpu(id->rd_msg->desc[0].len);

rd_msg points into the chunk buffer that the remote peer filled via
RDMA-WRITE-WITH-IMM (rtrs_srv_rdma_done() -> process_io_req() ->
process_read()), so desc[0].len is attacker-controlled and, before this
change, was only rejected when zero. The source address is the fixed
chunk start (dma_addr[msg_id]) and the source lkey is the PD-wide
local_dma_lkey, which is not tied to the chunk's MR mapping, so the verbs
layer does not constrain the transfer length to max_chunk_size. msg_id
and off are bounded against queue_depth and max_chunk_size in
rtrs_srv_rdma_done(), but desc[0].len is a separate field that was not
checked against the chunk size.

A peer that advertises desc[0].len larger than max_chunk_size can make
the posted RDMA write read past the chunk's mapped region. The resulting
behaviour depends on the IOMMU configuration: with no IOMMU or in
passthrough mode the read may extend into memory adjacent to the chunk
and be returned to the peer, which can disclose host memory; with a
translating IOMMU the out-of-range access is expected to fault and abort
the connection. In either case the transfer exceeds what the protocol
permits and is driven by a remote peer.

Reject a descriptor length above max_chunk_size, mirroring the existing
off >= max_chunk_size bound in rtrs_srv_rdma_done(). Legitimate clients
do not exceed it: the client sets desc[0].len to its MR length, which is
capped at the negotiated max_io_size (max_chunk_size - MAX_HDR_SIZE).

## Remediation

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