CVE-2021-47517 (GCVE-0-2021-47517)

Vulnerability from cvelistv5 – Published: 2024-05-24 15:09 – Updated: 2026-08-05 08:48
VLAI
Title
ethtool: do not perform operations on net devices being unregistered
Summary
In the Linux kernel, the following vulnerability has been resolved: ethtool: do not perform operations on net devices being unregistered There is a short period between a net device starts to be unregistered and when it is actually gone. In that time frame ethtool operations could still be performed, which might end up in unwanted or undefined behaviours[1]. Do not allow ethtool operations after a net device starts its unregistration. This patch targets the netlink part as the ioctl one isn't affected: the reference to the net device is taken and the operation is executed within an rtnl lock section and the net device won't be found after unregister. [1] For example adding Tx queues after unregister ends up in NULL pointer exceptions and UaFs, such as: BUG: KASAN: use-after-free in kobject_get+0x14/0x90 Read of size 1 at addr ffff88801961248c by task ethtool/755 CPU: 0 PID: 755 Comm: ethtool Not tainted 5.15.0-rc6+ #778 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/014 Call Trace: dump_stack_lvl+0x57/0x72 print_address_description.constprop.0+0x1f/0x140 kasan_report.cold+0x7f/0x11b kobject_get+0x14/0x90 kobject_add_internal+0x3d1/0x450 kobject_init_and_add+0xba/0xf0 netdev_queue_update_kobjects+0xcf/0x200 netif_set_real_num_tx_queues+0xb4/0x310 veth_set_channels+0x1c3/0x550 ethnl_set_channels+0x524/0x610
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-05-24 19:18 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6638 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 041b1c5d4a53e97fc9e029ae32469552ca12cb9b , < 7c26da3be1e9843a15b5318f90db8a564479d2ac (git)
Affected: 041b1c5d4a53e97fc9e029ae32469552ca12cb9b , < cfd719f04267108f5f5bf802b9d7de69e99a99f9 (git)
Affected: 041b1c5d4a53e97fc9e029ae32469552ca12cb9b , < dde91ccfa25fd58f64c397d91b81a4b393100ffa (git)
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Linux Linux Affected: 5.6
Unaffected: 0 , < 5.6 (semver)
Unaffected: 5.10.87 , ≤ 5.10.* (semver)
Unaffected: 5.15.8 , ≤ 5.15.* (semver)
Unaffected: 5.16 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-416"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-11-06T12:12:34+00:00",
      "cve": "CVE-2021-47517",
      "id": "CVE-2021-47517",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:fixed": "286",
      "product_status:known_affected": "38",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ethtool: do not perform operations on net devices being unregistered",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47517.json",
      "version": "3"
    },
    "vulnrichment": {
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              "dateUpdated": "2024-08-04T05:39:59.610Z",
              "orgId": "af854a3a-2127-422b-91ae-364da2661108",
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                ],
                "url": "https://git.kernel.org/stable/c/dde91ccfa25fd58f64c397d91b81a4b393100ffa"
              }
            ],
            "title": "CVE Program Container"
          },
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2021-47517",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2024-05-24T19:18:28.551288Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2024-05-24T19:18:32.218Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
                "net/ethtool/netlink.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
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                  "lessThan": "7c26da3be1e9843a15b5318f90db8a564479d2ac",
                  "status": "affected",
                  "version": "041b1c5d4a53e97fc9e029ae32469552ca12cb9b",
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
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                  "version": "5.6"
                },
                {
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                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
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                  "lessThanOrEqual": "5.10.*",
                  "status": "unaffected",
                  "version": "5.10.87",
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                },
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                  "status": "unaffected",
                  "version": "5.15.8",
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                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "5.16",
                  "versionType": "original_commit_for_fix"
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              ]
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          ],
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            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nethtool: do not perform operations on net devices being unregistered\n\nThere is a short period between a net device starts to be unregistered\nand when it is actually gone. In that time frame ethtool operations\ncould still be performed, which might end up in unwanted or undefined\nbehaviours[1].\n\nDo not allow ethtool operations after a net device starts its\nunregistration. This patch targets the netlink part as the ioctl one\nisn\u0027t affected: the reference to the net device is taken and the\noperation is executed within an rtnl lock section and the net device\nwon\u0027t be found after unregister.\n\n[1] For example adding Tx queues after unregister ends up in NULL\n    pointer exceptions and UaFs, such as:\n\n      BUG: KASAN: use-after-free in kobject_get+0x14/0x90\n      Read of size 1 at addr ffff88801961248c by task ethtool/755\n\n      CPU: 0 PID: 755 Comm: ethtool Not tainted 5.15.0-rc6+ #778\n      Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/014\n      Call Trace:\n       dump_stack_lvl+0x57/0x72\n       print_address_description.constprop.0+0x1f/0x140\n       kasan_report.cold+0x7f/0x11b\n       kobject_get+0x14/0x90\n       kobject_add_internal+0x3d1/0x450\n       kobject_init_and_add+0xba/0xf0\n       netdev_queue_update_kobjects+0xcf/0x200\n       netif_set_real_num_tx_queues+0xb4/0x310\n       veth_set_channels+0x1c3/0x550\n       ethnl_set_channels+0x524/0x610"
            }
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                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
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                  "value": "AV:L - The bug is triggered via the ethtool Generic Netlink interface (AF_NETLINK / ETHTOOL_MSG_*_SET), a local syscall path; the ioctl path is unaffected and there is no remote packet-processing entry.\nAC:L - An attacker who can create and delete a netdev (e.g. veth) and issue ethtool CHANNELS_SET controls both sides of the race: hold a ref via ethnl_parse_header_dev_get, unregister under rtnl (tearing down queue kobjects), then set channels after rtnl is free\u2014winning the window is attacker-driven and retryable.\nPR:L - CHANNELS_SET (and other SET ops that call ethnl_ops_begin) require GENL_UNS_ADMIN_PERM, i.e. CAP_NET_ADMIN in the network namespace\u2019s user_ns; with netnsok and unshare -Urn this is available to an unprivileged userns user, not real init-ns root.\nUI:N - The attacker creates the device, races unregister with ethtool SET, and triggers the UAF themselves; no separate victim action is required.\nS:U - Impact is kernel heap UAF / oops within the same host OS authority (ethtool/netdevice sysfs kobjects); this is not a VM escape, IOMMU bypass, or other cross-boundary compromise.\nC:H - The fix documents a KASAN use-after-free in kobject_get when adding Tx queues after unregister; per guidance a UAF yields a high confidentiality impact via heap reuse/read primitives.\nI:H - The same UAF on unregistered queues_kset/queue kobjects enables heap spray and corruption of adjacent objects, supporting write and control-flow hijacking primitives.\nA:H - The report shows KASAN UAF and NULL pointer exceptions from operating on unregistering devices, which can oops/panic the kernel and fully impact availability."
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        "assignerShortName": "Linux",
        "cveId": "CVE-2021-47517",
        "datePublished": "2024-05-24T15:09:30.675Z",
        "dateReserved": "2024-05-24T15:02:54.824Z",
        "dateUpdated": "2026-08-05T08:48:13.450Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
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  }
}



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