{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89738", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.761Z", "datePublished": "2026-09-11T19:46:45.898Z", "dateUpdated": "2026-10-19T08:51:52.252Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:51:52.252Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed\n\nIn polled-VBUS mode (board.vbus_pin && board.vbus_polled), probe arms a\nself-restarting cycle: at91_vbus_timer() schedules vbus_timer_work, and\nat91_vbus_timer_work() calls at91_vbus_update() and re-arms the timer via\nmod_timer(). Both recover the same udc through container_of and dereference\nit on every iteration.\n\nNeither teardown path cancels this cycle. udc is devm-allocated, so it is\nfreed after at91udc_remove() returns, and is likewise freed when probe\nfails and devres runs. A timer callback or work item that is pending or\nrunning at either point dereferences the freed udc.\n\nAdd at91_udc_shutdown_vbus_timer() and call it from at91udc_remove() and\nfrom the usb_add_gadget_udc() failure path in probe; the remaining probe\nerror paths fail before the timer is armed. timer_shutdown_sync() waits\nfor a running callback and clears timer->function, which makes the work\nhandler's mod_timer() a permanent no-op; cancel_work_sync() then drains\nany pending or running work whose re-arm attempt now does nothing. The\ntimer must be shut down first, since cancelling the work alone would let\nthe timer re-queue it. The guard mirrors probe: in IRQ mode the timer and\nwork_struct are never initialized.\n\nThis does not require a fault; a normal driver unbind can interleave with\nan already queued work item.\n\nThis issue was found by an in-house static analysis tool." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The use-after-free is reached on local AT91 UDC platform-driver teardown (sysfs unbind, rmmod, or probe-error unwind after the polled-VBUS timer is armed), not by parsing USB host packets. That matches other USB gadget/UDC teardown UAFs scored Local and is higher severity than Physical.\nAC:L - Once polled-VBUS mode is active, unbind or the usb_add_gadget_udc() failure path frees the devm-allocated udc while the self-restarting timer/work still hold it; the next timer tick or already-queued work then dereferences the freed object with no race the attacker cannot drive.\nPR:L - Highest reasonable exposure is a local account that manages the USB gadget/UDC on AT91 industrial, IoT, and embedded controllers, where platform unbind or gadget HAL access is often delegated beyond init-namespace root. Uncertain Low vs High, so Low per the overestimate rule.\nUI:N - The attacker initiates driver unbind, module unload, or a failing re-probe themselves; no separate victim action such as plugging a USB cable, mounting a filesystem, or opening a device node is required.\nS:U - The use-after-free corrupts the host kernel's struct at91_udc heap object within the same OS security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - at91_vbus_timer() and at91_vbus_timer_work() recover the freed udc via container_of and read vbus_pin, gadget state, and related fields; reclaiming that slab yields a classic UAF read/disclosure primitive.\nI:H - The dangling work calls at91_vbus_session()/pullup(), which write MMIO through udp_baseaddr and invoke caps->pullup and possibly driver->disconnect on the freed object, enabling heap corruption and control-flow hijack.\nA:H - Dereferencing the freed udc from timer or workqueue context causes a kernel oops or panic even without a full exploit, so availability impact is High." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/usb/gadget/udc/at91_udc.c" ], "versions": [ { "version": "4037242c4f5ff77afe61bf07ca1e8a99490219e5", "lessThan": "a2a602cb1e28d76a5398cec3fa21b0110385f501", "status": "affected", "versionType": "git" }, { "version": "4037242c4f5ff77afe61bf07ca1e8a99490219e5", "lessThan": "51a311eb97e91ce1aed3005cb71ccb2e30f8cce8", "status": "affected", "versionType": "git" }, { "version": "4037242c4f5ff77afe61bf07ca1e8a99490219e5", "lessThan": "557ef547d49ff5e6026a4d39bdd3113bd81d7688", "status": "affected", "versionType": "git" }, { "version": "4037242c4f5ff77afe61bf07ca1e8a99490219e5", "lessThan": "c27d13ce4bab80fbdf6523928071b6c24b37606c", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/usb/gadget/udc/at91_udc.c" ], "versions": [ { "version": "2.6.36", "status": "affected" }, { "version": "0", "lessThan": "2.6.36", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.109", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.36", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.36", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.36", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.36", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/a2a602cb1e28d76a5398cec3fa21b0110385f501" }, { "url": "https://git.kernel.org/stable/c/51a311eb97e91ce1aed3005cb71ccb2e30f8cce8" }, { "url": "https://git.kernel.org/stable/c/557ef547d49ff5e6026a4d39bdd3113bd81d7688" }, { "url": "https://git.kernel.org/stable/c/c27d13ce4bab80fbdf6523928071b6c24b37606c" } ], "title": "usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed", "x_generator": { "engine": "bippy-1.2.0" } } } }