{ "schema_version": "1.6.1", "id": "RPI-CVE-2024-26996", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2024-26996" ], "published": "2024-05-01T05:31:05Z", "summary": "usb: gadget: f_ncm: Fix UAF ncm object at re-bind after usb ep transport error", "details": "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(), 'in_ep' and/or 'out_ep' may not be enabled.\n\nAfter that, ncm_disable() is called to disable for ncm unbind\nbut gether_disconnect() is never called since 'in_ep' is not enabled.\n\nAs the result, ncm object is released in ncm unbind\nbut 'dev->port_usb' associated to 'ncm->port' 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->port_usb=ffffff9b179c3200\n --> error happens in usb_ep_enable().\n NCM: ncm_disable: ncm=ffffff9b179c3200\n --> no gether_disconnect() since ncm->port.in_ep->enabled is false.\n NCM: ncm_unbind: ncm unbind ncm=ffffff9b179c3200\n NCM: ncm_free: ncm free ncm=ffffff9b179c3200 <-- 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->port_usb=ffffff9b179c3200 <-- previous released ncm\n usb0: eth_start dev->port_usb=ffffff9b179c3200 <--\n eth_start_xmit()\n --> dev->wrap()\n Unable to handle kernel paging request at virtual address dead00000000014f\n\nThis patch addresses the issue by checking if 'ncm->netdev' is not NULL at\nncm_disable() to call gether_disconnect() to deassociate 'dev->port_usb'.\nIt's more reasonable to check 'ncm->netdev' to call gether_connect/disconnect\nrather than check 'ncm->port.in_ep->enabled' since it might not be enabled\nbut the gether connection might be established.", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, 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"ccf1586ad0663fa91238ac56abf6340d6d740d18", "upstream_version": "6.1.58", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.1.88" }, "1:6.1.63-1+rpt1": { "linux_commit": null, "upstream_version": "6.1.63", "assessment": "upstream version (no usable Linux commit)", "upstream_fixed": "6.1.88" }, "1:6.1.73-1+rpt1": { "linux_commit": null, "upstream_version": "6.1.73", "assessment": "upstream version (no usable Linux commit)", "upstream_fixed": "6.1.88" }, "1:6.6.20-1+rpt1": { "linux_commit": "6f16847710cc0502450788b9f12f0a14d3429668", "upstream_version": "6.6.20", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.6.29" }, "1:6.6.28-1+rpt1": { "linux_commit": "0c341f47adc3578cd5f817aa20ee2b7f9ae6b23e", "upstream_version": "6.6.28", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.6.29" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2024-26996" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/7f67c2020cb08499c400abf0fc32c65e4d9a09ca" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/0588bbbd718a8130b98c54518f1e0b569ce60a93" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/f356fd0cbd9c9cbd0854657a80d1608d0d732db3" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/7250326cbb1f4f90391ac511a126b936cefb5bb7" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/6334b8e4553cc69f51e383c9de545082213d785e" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T11:52:36Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.8, "cvss_v3_severity": "High", "scenario": "AV:L - Every step needed to reach and trigger the dangling `dev->port_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->wrap()`. 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->port_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->open(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." } } }