CVE-2026-81003

Full vulnerability record from the local CVENow database.

Description

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.

Severity

HIGH

CVSS score

8.1 (v3.1)

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-09-11 20:19:08.863000

Last modified

2026-10-19 09:17:33.500000

View original CVE JSON

{
  "id": "CVE-2026-81003",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-11T20:19:08.863",
  "lastModified": "2026-10-19T09:17:33.500",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/iucv: filter frames in afiucv_hs_rcv() by ingress device\n\nafiucv_hs_rcv() selects a socket from iucv_sk_list by matching four 8-byte\nname fields in the transport header alone. No check is made against the\nnet_device the frame arrived on.\n\nThis can cause a frame arriving on any netdev to be delivered to an AF_IUCV\nsocket. Three problems follow.\n\nFirst, a frame arriving over HiperSockets can be delivered to a socket\nbound to the classic z/VM IUCV transport, which has iucv->hs_dev == NULL.\niucv_sock_bind() takes the classic path whenever the requested userid\nmatches iucv_userid, even on a guest that also has a HiperSockets device\ncarrying the same identifier. The child socket created by\nafiucv_hs_callback_syn() for such a match inherits hs_dev = NULL and\ntransport = AF_IUCV_TRANS_HIPER, so the first send() on it returns -ENODEV.\nThe socket delivered to accept() is unusable.\n\nSecond, a frame arriving on one netdev can be delivered to a socket bound\nto a different IQD device. Which can lead to\n- Accept-queue exhaustion (DoS)\n- Attacker-controlled peer identity in the child socket\n- Data injection into existing sockets\n- Fabric noise on the IQD fabric, where bogus replies are sent\n- killing established connections\n\nThird, all AF_IUCV sockets live in init_net, as iucv_sock_alloc() calls\nsk_alloc(&init_net, ...). But even frames arriving on netdev devices in a\nnamespace can be delivered to an IUCV socket. So a process in an\nunprivileged user and network namespace holding only the CAP_NET_RAW\ncapability valid within that namespace can send a raw ETH_P_AF_IUCV frame\non its own lo device and have it matched against init_net sockets.\n\nFix all three by skipping any socket whose hs_dev does not match the\ningress device. A classic z/VM IUCV socket has hs_dev == NULL; the ingress\ndev is never NULL, so classic sockets are skipped automatically. An unbound\nHIPER socket also has hs_dev == NULL and is skipped. A bound HIPER socket\nis only reachable from the exact IQD device it was bound to. Because hs_dev\nis always a device in init_net (iucv_sock_bind() scans\nfor_each_netdev_rcu(&init_net, ...) exclusively), a frame whose ingress\ndevice belongs to another namespace never matches any socket.\n\nNote that AF_IUCV over HiperSockets provides no per-connection\nauthentication: no sequence numbers, no TLS, no nonce. The four name fields\nidentifying a connection are exchanged in plaintext on the shared\nHiperSockets segment (VCHID). Any host on the same HiperSockets segment\ncould spoof any frame type against an existing connection. That is a\nprotocol-level property unchanged by this patch. The fix reduces the attack\nsurface to peers present on the same HiperSockets segment."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "net/iucv/af_iucv.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "3881ac441f642d56503818123446f7298442236b",
              "lessThan": "639828ad4d374056167391dbaffd13dd5e5e5ddb",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "3881ac441f642d56503818123446f7298442236b",
              "lessThan": "92e5c281f1caa287bb58292f2687c9e3ff3aa23e",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "3881ac441f642d56503818123446f7298442236b",
              "lessThan": "712330f8a4293cfd97b0d62b7c7dc01862a16b98",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "3881ac441f642d56503818123446f7298442236b",
              "lessThan": "0a5af67e7184c6a0e155c317840bd64b37177af4",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "3881ac441f642d56503818123446f7298442236b",
              "lessThan": "dfac2936b83be00035ae176f8252e1c1e1de9207",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "3881ac441f642d56503818123446f7298442236b",
              "lessThan": "8e3763f1ccac3fc395f9af2b87114c023ced8a3f",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "3881ac441f642d56503818123446f7298442236b",
              "lessThan": "a7f0130a091724e69827ab58e74777a88747e892",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "3881ac441f642d56503818123446f7298442236b",
              "lessThan": "80230a18c164a4b5bbc048fe2768b219ac17bc5a",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "net/iucv/af_iucv.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "3.2",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "3.2",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.10.270",
              "lessThanOrEqual": "5.10.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.15.221",
              "lessThanOrEqual": "5.15.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.188",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.157",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.109",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.50",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.4",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.3",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
          "baseScore": 8.1,
          "baseSeverity": "HIGH",
          "attackVector": "ADJACENT_NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 5.2
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/0a5af67e7184c6a0e155c317840bd64b37177af4",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/639828ad4d374056167391dbaffd13dd5e5e5ddb",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/712330f8a4293cfd97b0d62b7c7dc01862a16b98",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/80230a18c164a4b5bbc048fe2768b219ac17bc5a",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/8e3763f1ccac3fc395f9af2b87114c023ced8a3f",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/92e5c281f1caa287bb58292f2687c9e3ff3aa23e",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/a7f0130a091724e69827ab58e74777a88747e892",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/dfac2936b83be00035ae176f8252e1c1e1de9207",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}