---
id: CVE-2026-46133
title: 'RDMA/rxe: Reject unknown opcodes before ICRC processing'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  RDMA/rxe: Reject unknown opcodes before ICRC processing

  Even after applying commit 7244491dab34 ("RDMA/rxe: Validate pad and ICRC
  before payload_size() in rxe_rcv"), 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'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 <
    318787fa7193bd79691f2ebce4e80cb6abd0faef
  - >-
    Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 <
    6a79b1ea0fcb2c998fda6a793050f66146e9cc42
  - >-
    Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 <
    599cfdf44c1701c581cd4a21f1e1e03f8dc3840b
  - >-
    Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 <
    e3dc3a2fb05f4ed49c7f20594c4c52350d032189
  - >-
    Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 <
    f8ee926431a7bbec2b10c1290664af2cb290b983
  - >-
    Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 <
    006a3a5f75345c6a0dbf13fd3ee01406e93b6733
  - >-
    Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 <
    6fa18025e5782afff91415fd5217b39c1e4837d7
  - >-
    Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 <
    4c6f86d85d03cdb33addce86aa69aa795ca6c47a
  - Linux 4.8
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-16T15:20:11.447368Z'
published: '2026-05-28'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:31:04.376Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-46133'
references:
  - url: 'https://git.kernel.org/stable/c/318787fa7193bd79691f2ebce4e80cb6abd0faef'
  - url: 'https://git.kernel.org/stable/c/6a79b1ea0fcb2c998fda6a793050f66146e9cc42'
  - url: 'https://git.kernel.org/stable/c/599cfdf44c1701c581cd4a21f1e1e03f8dc3840b'
  - url: 'https://git.kernel.org/stable/c/e3dc3a2fb05f4ed49c7f20594c4c52350d032189'
  - url: 'https://git.kernel.org/stable/c/f8ee926431a7bbec2b10c1290664af2cb290b983'
  - url: 'https://git.kernel.org/stable/c/006a3a5f75345c6a0dbf13fd3ee01406e93b6733'
  - url: 'https://git.kernel.org/stable/c/6fa18025e5782afff91415fd5217b39c1e4837d7'
  - url: 'https://git.kernel.org/stable/c/4c6f86d85d03cdb33addce86aa69aa795ca6c47a'
tags:
  - cve.org
epss: 0.00574
epssPercentile: 0.46227
ingestedAt: '2026-10-16T17:24:46.709Z'
---

## Overview

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

RDMA/rxe: Reject unknown opcodes before ICRC processing

Even after applying commit 7244491dab34 ("RDMA/rxe: Validate pad and ICRC
before payload_size() in rxe_rcv"), a single unauthenticated UDP packet
can still trigger panic.  That patch handled payload_size() underflow only
for valid opcodes with short packets, not for packets carrying an unknown
opcode.  The unknown-opcode OOB read described below predates that commit
and reaches back to the initial Soft RoCE driver.

The check added there reads

    pkt->paylen < header_size(pkt) + bth_pad(pkt) + RXE_ICRC_SIZE

where header_size(pkt) expands to rxe_opcode[pkt->opcode].length.  The
rxe_opcode[] array has 256 entries but is only populated for defined IB
opcodes; any other entry (for example opcode 0xff) is zero-initialized, so
length == 0 and the check degenerates to

    pkt->paylen < 0 + bth_pad(pkt) + RXE_ICRC_SIZE

which does not constrain pkt->paylen enough.  rxe_icrc_hdr() then computes

    rxe_opcode[pkt->opcode].length - RXE_BTH_BYTES

which underflows when length == 0 and passes a huge value to rxe_crc32(),
causing an out-of-bounds read of the skb payload.

Reproduced on v7.0-rc7 with that fix applied, QEMU/KVM with
CONFIG_RDMA_RXE=y and CONFIG_KASAN=y, after

    rdma link add rxe0 type rxe netdev eth0

A single 48-byte UDP packet to port 4791 with BTH opcode=0xff and
QPN=IB_MULTICAST_QPN triggers:

    BUG: KASAN: slab-out-of-bounds in crc32_le+0x115/0x170
    Read of size 1 at addr ...
    The buggy address is located 0 bytes to the right of
     allocated 704-byte region
    Call Trace:
     crc32_le+0x115/0x170
     rxe_icrc_hdr.isra.0+0x226/0x300
     rxe_icrc_check+0x13f/0x3a0
     rxe_rcv+0x6e1/0x16e0
     rxe_udp_encap_recv+0x20a/0x320
     udp_queue_rcv_one_skb+0x7ed/0x12c0

Subsequent packets with the same shape fault on unmapped memory and panic
the kernel.  The trigger requires only module load and "rdma link add"; no
QP, no connection, and no authentication.

Fix this by rejecting packets whose opcode has no rxe_opcode[] entry,
detected via the zero mask or zero length, before any length arithmetic
runs.

## Affected

- `Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < 318787fa7193bd79691f2ebce4e80cb6abd0faef`
- `Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < 6a79b1ea0fcb2c998fda6a793050f66146e9cc42`
- `Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < 599cfdf44c1701c581cd4a21f1e1e03f8dc3840b`
- `Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < e3dc3a2fb05f4ed49c7f20594c4c52350d032189`
- `Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < f8ee926431a7bbec2b10c1290664af2cb290b983`
- `Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < 006a3a5f75345c6a0dbf13fd3ee01406e93b6733`
- `Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < 6fa18025e5782afff91415fd5217b39c1e4837d7`
- `Linux >= 8700e3e7c4857d28ebaa824509934556da0b3e76 < 4c6f86d85d03cdb33addce86aa69aa795ca6c47a`
- `Linux 4.8`

## Remediation

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