Skip to content
Fencer Vulns
high 8.1

CVE-2026-81003 json

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

published 2026-09-11 58 d ago modified 2026-10-19 21 d ago also EUVD-2026-76326

cvss
8.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 23%
public exploits
0
none known

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 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.

Patch / fix

  • Linux Linux 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, 6.18.50, 7.2.4, 7.3
  • linux Debian 12 6.1.190-1
  • linux Debian 13 6.12.111-1
  • linux Debian 14 7.2.6-1
  • linux-6.12 Debian 12 6.12.111-1~deb12u1

debian advisories DEBIAN-CVE-2026-81003

  • linux Ubuntu 22.04 LTS 5.15.0-202.212
  • linux Ubuntu 26.04 LTS 7.0.0-42.42
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1119.126
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1016.17
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1120.130
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1016.18
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1115.121
  • linux-ibm Ubuntu 22.04 LTS 5.15.0-1113.117

ubuntu advisories UBUNTU-CVE-2026-81003

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 9 5.14.0-687.58.1.el9_8
  • rv RHEL 9 5.14.0-687.58.1.el9_8
  • perf RHEL 9 5.14.0-687.58.1.el9_8
  • rtla RHEL 9 5.14.0-687.58.1.el9_8
  • libperf RHEL 9 5.14.0-687.58.1.el9_8
  • kernel-rt RHEL 9 5.14.0-687.58.1.el9_8
  • kernel-64k RHEL 9 5.14.0-687.58.1.el9_8
  • kernel-core RHEL 9 5.14.0-687.58.1.el9_8

red hat advisories RHSA-2026:83156

  • kernel-source openSUSE Tumbleweed 7.2.6-1.1

opensuse advisories openSUSE-SU-2026:11805-1

  • kernel-rt AlmaLinux 8 4.18.0-553.178.1.rt7.519.el8_10
  • kernel-rt-core AlmaLinux 8 4.18.0-553.178.1.rt7.519.el8_10
  • kernel-rt-modules AlmaLinux 8 4.18.0-553.178.1.rt7.519.el8_10
  • kernel-rt-debug-core AlmaLinux 8 4.18.0-553.178.1.rt7.519.el8_10
  • kernel-rt-debug-modules AlmaLinux 8 4.18.0-553.178.1.rt7.519.el8_10
  • kernel-rt-modules-extra AlmaLinux 8 4.18.0-553.178.1.rt7.519.el8_10
  • kernel-rt-debug-modules-extra AlmaLinux 8 4.18.0-553.178.1.rt7.519.el8_10
  • kernel AlmaLinux 8 4.18.0-553.178.1.el8_10

almalinux advisories ALSA-2026:89082ALSA-2026:89083ALSA-2026:83156

  • kernel-rt Rocky Linux 8 4.18.0-553.178.1.rt7.519.el8_10
  • kernel Rocky Linux 8 4.18.0-553.178.1.el8_10
  • kernel Rocky Linux 9 5.14.0-687.58.1.el9_8

rocky linux advisories RLSA-2026:89082RLSA-2026:89083RLSA-2026:83156

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-81003 updated cvss 7.8

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

  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more Red Hat Enterprise Linux 10 kernel Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    under investigation
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.58.1.el9_8, perf 5.14.0-687.58.1.el9_8, rtla 5.14.0-687.58.1.el9_8, python3-perf 5.14.0-687.58.1.el9_8, kernel-devel-matched 5.14.0-687.58.1.el9_8, kernel-64k-devel-matched 5.14.0-687.58.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:83156
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.178.1.el8_10, kernel 4.18.0-553.178.1.el8_10, bpftool 4.18.0-553.178.1.el8_10, kernel-core 4.18.0-553.178.1.el8_10, kernel-tools 4.18.0-553.178.1.el8_10, python3-perf 4.18.0-553.178.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:89083
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.58.1.el9_8, kernel-64k 5.14.0-687.58.1.el9_8, kernel-core 5.14.0-687.58.1.el9_8, kernel-tools 5.14.0-687.58.1.el9_8, kernel-modules 5.14.0-687.58.1.el9_8, kernel-64k-core 5.14.0-687.58.1.el9_8, +27 more Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.58.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.58.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.58.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.58.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.58.1.el9_8
    fixed: vendor fix RHSA-2026:83156
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.178.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.178.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.178.1.el8_10
    fixed: vendor fix RHSA-2026:89083
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.178.1.rt7.519.el8_10, kernel-rt-kvm 4.18.0-553.178.1.rt7.519.el8_10, kernel-rt-core 4.18.0-553.178.1.rt7.519.el8_10, kernel-rt-modules 4.18.0-553.178.1.rt7.519.el8_10, kernel-rt-debug-kvm 4.18.0-553.178.1.rt7.519.el8_10, kernel-rt-debug-core 4.18.0-553.178.1.rt7.519.el8_10, +4 more
    fixed: vendor fix RHSA-2026:89082
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.58.1.el9_8, kernel-rt-64k 5.14.0-687.58.1.el9_8, kernel-rt-core 5.14.0-687.58.1.el9_8, kernel-rt-modules 5.14.0-687.58.1.el9_8, kernel-rt-64k-core 5.14.0-687.58.1.el9_8, kernel-rt-debug-core 5.14.0-687.58.1.el9_8, +14 more Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.58.1.el9_8, kernel-rt-core 5.14.0-687.58.1.el9_8, kernel-rt-modules 5.14.0-687.58.1.el9_8, kernel-rt-debug-core 5.14.0-687.58.1.el9_8, kernel-rt-modules-core 5.14.0-687.58.1.el9_8, kernel-rt-debug-modules 5.14.0-687.58.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:83156
show 2 more
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.178.1.rt7.519.el8_10, kernel-rt-core 4.18.0-553.178.1.rt7.519.el8_10, kernel-rt-modules 4.18.0-553.178.1.rt7.519.el8_10, kernel-rt-debug-core 4.18.0-553.178.1.rt7.519.el8_10, kernel-rt-debug-modules 4.18.0-553.178.1.rt7.519.el8_10, kernel-rt-modules-extra 4.18.0-553.178.1.rt7.519.el8_10, +2 more
    fixed: vendor fix RHSA-2026:89082
  • Red Hat OpenShift Container Platform 4.22 rhcos 4.22.9.8.202610241758
    fixed: vendor fix RHSA-2026:89197

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.31% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.1 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.