CVE-2024-26996 (GCVE-0-2024-26996)
Vulnerability from cvelistv5
Published
2024-05-01 05:28
Modified
2026-08-05 11:28
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_ncm: Fix UAF ncm object at re-bind after usb ep transport error When ncm function is working and then stop usb0 interface for link down, eth_stop() is called. At this piont, accidentally if usb transport error should happen in usb_ep_enable(), 'in_ep' and/or 'out_ep' may not be enabled. After that, ncm_disable() is called to disable for ncm unbind but gether_disconnect() is never called since 'in_ep' is not enabled. As the result, ncm object is released in ncm unbind but 'dev->port_usb' associated to 'ncm->port' is not NULL. And when ncm bind again to recover netdev, ncm object is reallocated but usb0 interface is already associated to previous released ncm object. Therefore, once usb0 interface is up and eth_start_xmit() is called, released ncm object is dereferrenced and it might cause use-after-free memory. [function unlink via configfs] usb0: eth_stop dev->port_usb=ffffff9b179c3200 --> error happens in usb_ep_enable(). NCM: ncm_disable: ncm=ffffff9b179c3200 --> no gether_disconnect() since ncm->port.in_ep->enabled is false. NCM: ncm_unbind: ncm unbind ncm=ffffff9b179c3200 NCM: ncm_free: ncm free ncm=ffffff9b179c3200 <-- released ncm [function link via configfs] NCM: ncm_alloc: ncm alloc ncm=ffffff9ac4f8a000 NCM: ncm_bind: ncm bind ncm=ffffff9ac4f8a000 NCM: ncm_set_alt: ncm=ffffff9ac4f8a000 alt=0 usb0: eth_open dev->port_usb=ffffff9b179c3200 <-- previous released ncm usb0: eth_start dev->port_usb=ffffff9b179c3200 <-- eth_start_xmit() --> dev->wrap() Unable to handle kernel paging request at virtual address dead00000000014f This patch addresses the issue by checking if 'ncm->netdev' is not NULL at ncm_disable() to call gether_disconnect() to deassociate 'dev->port_usb'. It's more reasonable to check 'ncm->netdev' to call gether_connect/disconnect rather than check 'ncm->port.in_ep->enabled' since it might not be enabled but the gether connection might be established.
References
Impacted products
Vendor Product Version
Linux Linux Version: 6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b
Version: 6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b
Version: 6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b
Version: 6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b
Version: 6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_ncm: Fix UAF ncm object at re-bind after usb ep transport error\n\nWhen ncm function is working and then stop usb0 interface for link down,\neth_stop() is called. At this piont, accidentally if usb transport error\nshould happen in usb_ep_enable(), \u0027in_ep\u0027 and/or \u0027out_ep\u0027 may not be enabled.\n\nAfter that, ncm_disable() is called to disable for ncm unbind\nbut gether_disconnect() is never called since \u0027in_ep\u0027 is not enabled.\n\nAs the result, ncm object is released in ncm unbind\nbut \u0027dev-\u003eport_usb\u0027 associated to \u0027ncm-\u003eport\u0027 is not NULL.\n\nAnd when ncm bind again to recover netdev, ncm object is reallocated\nbut usb0 interface is already associated to previous released ncm object.\n\nTherefore, once usb0 interface is up and eth_start_xmit() is called,\nreleased ncm object is dereferrenced and it might cause use-after-free memory.\n\n[function unlink via configfs]\n  usb0: eth_stop dev-\u003eport_usb=ffffff9b179c3200\n  --\u003e error happens in usb_ep_enable().\n  NCM: ncm_disable: ncm=ffffff9b179c3200\n  --\u003e no gether_disconnect() since ncm-\u003eport.in_ep-\u003eenabled is false.\n  NCM: ncm_unbind: ncm unbind ncm=ffffff9b179c3200\n  NCM: ncm_free: ncm free ncm=ffffff9b179c3200   \u003c-- released ncm\n\n[function link via configfs]\n  NCM: ncm_alloc: ncm alloc ncm=ffffff9ac4f8a000\n  NCM: ncm_bind: ncm bind ncm=ffffff9ac4f8a000\n  NCM: ncm_set_alt: ncm=ffffff9ac4f8a000 alt=0\n  usb0: eth_open dev-\u003eport_usb=ffffff9b179c3200  \u003c-- previous released ncm\n  usb0: eth_start dev-\u003eport_usb=ffffff9b179c3200 \u003c--\n  eth_start_xmit()\n  --\u003e dev-\u003ewrap()\n  Unable to handle kernel paging request at virtual address dead00000000014f\n\nThis patch addresses the issue by checking if \u0027ncm-\u003enetdev\u0027 is not NULL at\nncm_disable() to call gether_disconnect() to deassociate \u0027dev-\u003eport_usb\u0027.\nIt\u0027s more reasonable to check \u0027ncm-\u003enetdev\u0027 to call gether_connect/disconnect\nrather than check \u0027ncm-\u003eport.in_ep-\u003eenabled\u0027 since it might not be enabled\nbut the gether connection might be established."
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              "value": "AV:L - Every step needed to reach and trigger the dangling `dev-\u003eport_usb` is a local operation \u2014 configfs gadget function unlink/relink, `ip link set usb0 down/up`, and a packet transmit on usb0 that reaches `eth_start_xmit()`/`dev-\u003ewrap()`. No physical USB host interaction is required for the freed `f_ncm` to be dereferenced, and on dummy_hcd-style setups even the host side is driven locally.\nAC:L - The attacker drives both sides of the sequence and can repeat it indefinitely (loop link down/up plus function unlink/relink), and the `eth_stop()` path that leaves `in_ep` disabled while the gether link stays associated is reachable via the carrier window in `gether_connect()` as well as any `usb_ep_enable()` failure. Freed-object reclaim of a plain kmalloc slab is standard and reliable.\nPR:L - The gadget/netdev reconfiguration is administrative, but on the affected NCM/tethering deployments those interfaces are delegated to low-privilege system components and the netdev can live in a delegated netns where CAP_NET_ADMIN is obtainable via user namespaces; the final use-after-free dereference in `eth_start_xmit()` is reached by any unprivileged local user simply sending traffic on usb0.\nUI:N - No action by another user is required \u2014 the attacker performs the whole sequence, and once the interface is brought up the stale pointer is dereferenced automatically by IPv6 DAD/RA or any queued transmit.\nS:U - The use-after-free is confined to kernel memory in the same security authority; there is no VM, IOMMU, or sandbox boundary crossed.\nC:H - The freed `f_ncm` is reached through `dev-\u003eport_usb` and its fields (`parser_opts`, `cdc_filter`, `skb_tx_data/ndp`, `fixed_in_len`) are used for length arithmetic and buffer construction in `ncm_wrap_ntb`, so a reclaimed slab gives an attacker-controlled read primitive and kernel memory disclosure through transmitted frames.\nI:H - `eth_open()` performs `link-\u003eopen(link)` \u2014 an indirect call through a function pointer stored inside the freed object \u2014 and `ncm_wrap_ntb` writes using attacker-controlled offsets from the reclaimed allocation, providing arbitrary write and control-flow hijack suitable for privilege escalation.\nA:H - The commit log documents the resulting kernel oops (\"Unable to handle kernel paging request at virtual address dead00000000014f\"); any unmitigated dereference of the freed ncm object panics the kernel."
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    "cveId": "CVE-2024-26996",
    "datePublished": "2024-05-01T05:28:16.652Z",
    "dateReserved": "2024-02-19T14:20:24.206Z",
    "dateUpdated": "2026-08-05T11:28:54.861Z",
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No physical USB host interaction is required for the freed `f_ncm` to be dereferenced, and on dummy_hcd-style setups even the host side is driven locally.\\nAC:L - The attacker drives both sides of the sequence and can repeat it indefinitely (loop link down/up plus function unlink/relink), and the `eth_stop()` path that leaves `in_ep` disabled while the gether link stays associated is reachable via the carrier window in `gether_connect()` as well as any `usb_ep_enable()` failure. Freed-object reclaim of a plain kmalloc slab is standard and reliable.\\nPR:L - The gadget/netdev reconfiguration is administrative, but on the affected NCM/tethering deployments those interfaces are delegated to low-privilege system components and the netdev can live in a delegated netns where CAP_NET_ADMIN is obtainable via user namespaces; the final use-after-free dereference in `eth_start_xmit()` is reached by any unprivileged local user simply sending traffic on usb0.\\nUI:N - No action by another user is required \\u2014 the attacker performs the whole sequence, and once the interface is brought up the stale pointer is dereferenced automatically by IPv6 DAD/RA or any queued transmit.\\nS:U - The use-after-free is confined to kernel memory in the same security authority; there is no VM, IOMMU, or sandbox boundary crossed.\\nC:H - The freed `f_ncm` is reached through `dev-\u003eport_usb` and its fields (`parser_opts`, `cdc_filter`, `skb_tx_data/ndp`, `fixed_in_len`) are used for length arithmetic and buffer construction in `ncm_wrap_ntb`, so a reclaimed slab gives an attacker-controlled read primitive and kernel memory disclosure through transmitted frames.\\nI:H - `eth_open()` performs `link-\u003eopen(link)` \\u2014 an indirect call through a function pointer stored inside the freed object \\u2014 and `ncm_wrap_ntb` writes using attacker-controlled offsets from the reclaimed allocation, providing arbitrary write and control-flow hijack suitable for privilege escalation.\\nA:H - The commit log documents the resulting kernel oops (\\\"Unable to handle kernel paging request at virtual address dead00000000014f\\\"); any unmitigated dereference of the freed ncm object panics the kernel.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b\", \"lessThan\": \"7f67c2020cb08499c400abf0fc32c65e4d9a09ca\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b\", \"lessThan\": \"0588bbbd718a8130b98c54518f1e0b569ce60a93\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b\", \"lessThan\": \"f356fd0cbd9c9cbd0854657a80d1608d0d732db3\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b\", \"lessThan\": \"7250326cbb1f4f90391ac511a126b936cefb5bb7\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b\", \"lessThan\": \"6334b8e4553cc69f51e383c9de545082213d785e\", \"versionType\": \"git\"}], \"programFiles\": [\"drivers/usb/gadget/function/f_ncm.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"4.4\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"4.4\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.15.157\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"6.1.88\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.29\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.8.8\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.8.*\"}, {\"status\": \"unaffected\", \"version\": \"6.9\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"drivers/usb/gadget/function/f_ncm.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/7f67c2020cb08499c400abf0fc32c65e4d9a09ca\"}, {\"url\": \"https://git.kernel.org/stable/c/0588bbbd718a8130b98c54518f1e0b569ce60a93\"}, {\"url\": \"https://git.kernel.org/stable/c/f356fd0cbd9c9cbd0854657a80d1608d0d732db3\"}, {\"url\": \"https://git.kernel.org/stable/c/7250326cbb1f4f90391ac511a126b936cefb5bb7\"}, {\"url\": \"https://git.kernel.org/stable/c/6334b8e4553cc69f51e383c9de545082213d785e\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nusb: gadget: f_ncm: Fix UAF ncm object at re-bind after usb ep transport error\\n\\nWhen ncm function is working and then stop usb0 interface for link down,\\neth_stop() is called. At this piont, accidentally if usb transport error\\nshould happen in usb_ep_enable(), \u0027in_ep\u0027 and/or \u0027out_ep\u0027 may not be enabled.\\n\\nAfter that, ncm_disable() is called to disable for ncm unbind\\nbut gether_disconnect() is never called since \u0027in_ep\u0027 is not enabled.\\n\\nAs the result, ncm object is released in ncm unbind\\nbut \u0027dev-\u003eport_usb\u0027 associated to \u0027ncm-\u003eport\u0027 is not NULL.\\n\\nAnd when ncm bind again to recover netdev, ncm object is reallocated\\nbut usb0 interface is already associated to previous released ncm object.\\n\\nTherefore, once usb0 interface is up and eth_start_xmit() is called,\\nreleased ncm object is dereferrenced and it might cause use-after-free memory.\\n\\n[function unlink via configfs]\\n  usb0: eth_stop dev-\u003eport_usb=ffffff9b179c3200\\n  --\u003e error happens in usb_ep_enable().\\n  NCM: ncm_disable: ncm=ffffff9b179c3200\\n  --\u003e no gether_disconnect() since ncm-\u003eport.in_ep-\u003eenabled is false.\\n  NCM: ncm_unbind: ncm unbind ncm=ffffff9b179c3200\\n  NCM: ncm_free: ncm free ncm=ffffff9b179c3200   \u003c-- released ncm\\n\\n[function link via configfs]\\n  NCM: ncm_alloc: ncm alloc ncm=ffffff9ac4f8a000\\n  NCM: ncm_bind: ncm bind ncm=ffffff9ac4f8a000\\n  NCM: ncm_set_alt: ncm=ffffff9ac4f8a000 alt=0\\n  usb0: eth_open dev-\u003eport_usb=ffffff9b179c3200  \u003c-- previous released ncm\\n  usb0: eth_start dev-\u003eport_usb=ffffff9b179c3200 \u003c--\\n  eth_start_xmit()\\n  --\u003e dev-\u003ewrap()\\n  Unable to handle kernel paging request at virtual address dead00000000014f\\n\\nThis patch addresses the issue by checking if \u0027ncm-\u003enetdev\u0027 is not NULL at\\nncm_disable() to call gether_disconnect() to deassociate \u0027dev-\u003eport_usb\u0027.\\nIt\u0027s more reasonable to check \u0027ncm-\u003enetdev\u0027 to call gether_connect/disconnect\\nrather than check \u0027ncm-\u003eport.in_ep-\u003eenabled\u0027 since it might not be enabled\\nbut the gether connection might be established.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.157\", \"versionStartIncluding\": \"4.4\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.88\", \"versionStartIncluding\": \"4.4\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.29\", \"versionStartIncluding\": \"4.4\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.8.8\", \"versionStartIncluding\": \"4.4\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.9\", \"versionStartIncluding\": \"4.4\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-05T11:28:54.861Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2024-26996\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T11:28:54.861Z\", \"dateReserved\": \"2024-02-19T14:20:24.206Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-05-01T05:28:16.652Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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