openvswitch: cap upcall PID array size and pre-size vport replies

{
  "id": "c77c9c763ccc74337c22880b0c218f904ddf31097c675a2df4d6ff385998f38b",
  "url": "https://osv.dev/vulnerability/CVE-2026-45840",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "openvswitch: cap upcall PID array size and pre-size vport replies",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: openvswitch: cap upcall PID array size and pre-size vport replies The vport netlink reply helpers allocate a fixed-size skb with nlmsg_new(NLMSG_DEFAULT_SIZE, ...) but serialize the full upcall PID array via ovs_vport_get_upcall_portids(). Since ovs_vport_set_upcall_portids() accepts any non-zero multiple of sizeof(u32) with no upper bound, a CAP_NET_ADMIN user can install a PID array large enough to overflow the reply buffer, causing nla_put() to fail with -EMSGSIZE and hitting BUG_ON(err < 0). On systems with unprivileged user namespaces enabled (e.g., Ubuntu default), this is reachable via unshare -Urn since OVS vport mutation operations use GENL_UNS_ADMIN_PERM. kernel BUG at net/openvswitch/datapath.c:2414! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI CPU: 1 UID: 0 PID: 65 Comm: poc Not tainted 7.0.0-rc7-00195-geb216e422044 #1 RIP: 0010:ovs_vport_cmd_set+0x34c/0x400 Call Trace: genl_family_rcv_msg_doit (net/netlink/genetlink.c:1116) genl_rcv_msg (net/netlink/genetlink.c:1194) netlink_rcv_skb (net/netlink/af_netlink.c:2550) genl_rcv (net/netlink/genetlink.c:1219) netlink_unicast (net/netlink/af_netlink.c:1344) netlink_sendmsg (net/netlink/af_netlink.c:1894) __sys_sendto (net/socket.c:2206) __x64_sys_sendto (net/socket.c:2209) do_syscall_64 (arch/x86/entry/syscall_64.c:63) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Kernel panic - not syncing: Fatal exception Reject attempts to set mor",
    "evidence": "osv:CVE-2026-45840",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.258",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.209",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.175",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.141",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.91",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.33",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.0.10",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-45840",
      "aliases": [
        "CVE-2026-45840"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "5cd667b0a4567048bb555927d6ee564f4e5620a9"
                },
                {
                  "fixed": "8d59b80e69dddb665eb2de36e62859ab2073470e"
                },
                {
                  "fixed": "d9e47e29aacb9f8a9d59feb6ab5b128a9bbb40b0"
                },
                {
                  "fixed": "b39f763d720d623218bc1d95ace6855d7b474e81"
                },
                {
                  "fixed": "f9ef3db77a383d66847fd082c2b437d8ae4d9c63"
                },
                {
                  "fixed": "f99ac36b5d7c719d08a69fcdecce40f78a874e15"
                },
                {
                  "fixed": "fa6e90bc443bed8dc0d55bc5ea5b27ffdfe37704"
                },
                {
                  "fixed": "1d6c02b86329883aa467a3a61f8d34369db73a2f"
                },
                {
                  "fixed": "2091c6aa0df6aba47deb5c8ab232b1cb60af3519"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-45840.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "3.17.0"
                },
                {
                  "fixed": "5.10.258"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.11.0"
                },
                {
                  "fixed": "5.15.209"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.175"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.141"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.91"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.33"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.0.10"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-45840.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:38.001181318Z",
      "provider": "osv",
      "references": [
        "https://cert-portal.siemens.com/productcert/html/ssa-784472.html",
        "https://git.kernel.org/stable/c/1d6c02b86329883aa467a3a61f8d34369db73a2f",
        "https://git.kernel.org/stable/c/2091c6aa0df6aba47deb5c8ab232b1cb60af3519",
        "https://git.kernel.org/stable/c/8d59b80e69dddb665eb2de36e62859ab2073470e",
        "https://git.kernel.org/stable/c/b39f763d720d623218bc1d95ace6855d7b474e81",
        "https://git.kernel.org/stable/c/d9e47e29aacb9f8a9d59feb6ab5b128a9bbb40b0",
        "https://git.kernel.org/stable/c/f99ac36b5d7c719d08a69fcdecce40f78a874e15",
        "https://git.kernel.org/stable/c/f9ef3db77a383d66847fd082c2b437d8ae4d9c63",
        "https://git.kernel.org/stable/c/fa6e90bc443bed8dc0d55bc5ea5b27ffdfe37704",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45840.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-45840",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45840.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-45840",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 505011,
  "published_at": "2026-05-27T09:24:39.478+00:00"
}