---
id: CVE-2026-81003
title: 'net/iucv: filter frames in afiucv_hs_rcv() by ingress device'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/iucv: filter frames in afiucv_hs_rcv() by ingress device

  afiucv_hs_rcv() selects a socket from iucv_sk_list by matching four 8-byte
  name fields in the transport he…
severity: high
cvss: 8.1
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 3881ac441f642d56503818123446f7298442236b <
    639828ad4d374056167391dbaffd13dd5e5e5ddb
  - >-
    Linux >= 3881ac441f642d56503818123446f7298442236b <
    92e5c281f1caa287bb58292f2687c9e3ff3aa23e
  - >-
    Linux >= 3881ac441f642d56503818123446f7298442236b <
    712330f8a4293cfd97b0d62b7c7dc01862a16b98
  - >-
    Linux >= 3881ac441f642d56503818123446f7298442236b <
    0a5af67e7184c6a0e155c317840bd64b37177af4
  - >-
    Linux >= 3881ac441f642d56503818123446f7298442236b <
    dfac2936b83be00035ae176f8252e1c1e1de9207
  - >-
    Linux >= 3881ac441f642d56503818123446f7298442236b <
    8e3763f1ccac3fc395f9af2b87114c023ced8a3f
  - >-
    Linux >= 3881ac441f642d56503818123446f7298442236b <
    a7f0130a091724e69827ab58e74777a88747e892
  - >-
    Linux >= 3881ac441f642d56503818123446f7298442236b <
    80230a18c164a4b5bbc048fe2768b219ac17bc5a
  - Linux 3.2
published: '2026-09-11'
updated: '2026-09-14'
sourceUpdated: '2026-09-14T11:59:38.541Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-81003'
references:
  - url: 'https://git.kernel.org/stable/c/639828ad4d374056167391dbaffd13dd5e5e5ddb'
  - url: 'https://git.kernel.org/stable/c/92e5c281f1caa287bb58292f2687c9e3ff3aa23e'
  - url: 'https://git.kernel.org/stable/c/712330f8a4293cfd97b0d62b7c7dc01862a16b98'
  - url: 'https://git.kernel.org/stable/c/0a5af67e7184c6a0e155c317840bd64b37177af4'
  - url: 'https://git.kernel.org/stable/c/dfac2936b83be00035ae176f8252e1c1e1de9207'
  - url: 'https://git.kernel.org/stable/c/8e3763f1ccac3fc395f9af2b87114c023ced8a3f'
  - url: 'https://git.kernel.org/stable/c/a7f0130a091724e69827ab58e74777a88747e892'
  - url: 'https://git.kernel.org/stable/c/80230a18c164a4b5bbc048fe2768b219ac17bc5a'
tags:
  - cve.org
epss: 0.00313
epssPercentile: 0.24478
ingestedAt: '2026-09-14T15:23:07.454Z'
---

## Overview

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

net/iucv: filter frames in afiucv_hs_rcv() by ingress device

afiucv_hs_rcv() selects a socket from iucv_sk_list by matching four 8-byte
name fields in the transport header alone. No check is made against the
net_device the frame arrived on.

This can cause a frame arriving on any netdev to be delivered to an AF_IUCV
socket. Three problems follow.

First, a frame arriving over HiperSockets can be delivered to a socket
bound to the classic z/VM IUCV transport, which has iucv->hs_dev == NULL.
iucv_sock_bind() takes the classic path whenever the requested userid
matches iucv_userid, even on a guest that also has a HiperSockets device
carrying the same identifier. The child socket created by
afiucv_hs_callback_syn() for such a match inherits hs_dev = NULL and
transport = AF_IUCV_TRANS_HIPER, so the first send() on it returns -ENODEV.
The socket delivered to accept() is unusable.

Second, a frame arriving on one netdev can be delivered to a socket bound
to a different IQD device. Which can lead to
- Accept-queue exhaustion (DoS)
- Attacker-controlled peer identity in the child socket
- Data injection into existing sockets
- Fabric noise on the IQD fabric, where bogus replies are sent
- killing established connections

Third, all AF_IUCV sockets live in init_net, as iucv_sock_alloc() calls
sk_alloc(&init_net, ...). But even frames arriving on netdev devices in a
namespace can be delivered to an IUCV socket. So a process in an
unprivileged user and network namespace holding only the CAP_NET_RAW
capability valid within that namespace can send a raw ETH_P_AF_IUCV frame
on its own lo device and have it matched against init_net sockets.

Fix all three by skipping any socket whose hs_dev does not match the
ingress device. A classic z/VM IUCV socket has hs_dev == NULL; the ingress
dev is never NULL, so classic sockets are skipped automatically. An unbound
HIPER socket also has hs_dev == NULL and is skipped. A bound HIPER socket
is only reachable from the exact IQD device it was bound to. Because hs_dev
is always a device in init_net (iucv_sock_bind() scans
for_each_netdev_rcu(&init_net, ...) exclusively), a frame whose ingress
device belongs to another namespace never matches any socket.

Note that AF_IUCV over HiperSockets provides no per-connection
authentication: no sequence numbers, no TLS, no nonce. The four name fields
identifying a connection are exchanged in plaintext on the shared
HiperSockets segment (VCHID). Any host on the same HiperSockets segment
could spoof any frame type against an existing connection. That is a
protocol-level property unchanged by this patch. The fix reduces the attack
surface to peers present on the same HiperSockets segment.

## Affected

- `Linux >= 3881ac441f642d56503818123446f7298442236b < 639828ad4d374056167391dbaffd13dd5e5e5ddb`
- `Linux >= 3881ac441f642d56503818123446f7298442236b < 92e5c281f1caa287bb58292f2687c9e3ff3aa23e`
- `Linux >= 3881ac441f642d56503818123446f7298442236b < 712330f8a4293cfd97b0d62b7c7dc01862a16b98`
- `Linux >= 3881ac441f642d56503818123446f7298442236b < 0a5af67e7184c6a0e155c317840bd64b37177af4`
- `Linux >= 3881ac441f642d56503818123446f7298442236b < dfac2936b83be00035ae176f8252e1c1e1de9207`
- `Linux >= 3881ac441f642d56503818123446f7298442236b < 8e3763f1ccac3fc395f9af2b87114c023ced8a3f`
- `Linux >= 3881ac441f642d56503818123446f7298442236b < a7f0130a091724e69827ab58e74777a88747e892`
- `Linux >= 3881ac441f642d56503818123446f7298442236b < 80230a18c164a4b5bbc048fe2768b219ac17bc5a`
- `Linux 3.2`

## Remediation

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