201 lines
12 KiB
JSON
201 lines
12 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-72071",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2026-08-09T03:40:39.904Z",
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"datePublished": "2026-08-15T05:52:23.215Z",
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"dateUpdated": "2026-08-17T05:40:01.974Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-08-17T05:40:01.974Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing/user_events: Fix use-after-free in user_event_mm_dup()\n\nuser_event_mm_dup() walks the parent mm's enabler list locklessly under\nrcu_read_lock() during fork() (from copy_process()); it does not take\nevent_mutex:\n\n\trcu_read_lock();\n\tlist_for_each_entry_rcu(enabler, &old_mm->enablers, mm_enablers_link)\n\t\tenabler->event = user_event_get(orig->event);\n\nuser_event_enabler_destroy() removes an enabler from that list with\nlist_del_rcu() and then, without waiting for a grace period, drops the\nenabler's user_event reference with user_event_put() and frees the enabler\nwith kfree(). A reader that loaded the enabler before the list_del_rcu()\ncan still be walking it, which leads to two use-after-frees:\n\n - kfree(enabler) frees the enabler while that reader dereferences\n enabler->event.\n\n - user_event_put() may drop the last reference to the user_event, which\n is then freed (via delayed_destroy_user_event() on a work queue), while\n the same reader does user_event_get(orig->event) on it.\n\nBoth are reachable by an unprivileged task that can open user_events_data:\none multithreaded process that registers an enabler and then concurrently\nunregisters it and calls fork() triggers the race. KASAN reports a\nslab-use-after-free in user_event_mm_dup() during clone(), with a\n\"refcount_t: addition on 0\" warning when the user_event is freed.\n\nThe enabler use-after-free was found first; the user_event one was reported\nby XIAO WU, and the earlier enabler-only fix did not address it.\n\nDefer both the user_event_put() and the kfree(enabler) to a work item\nqueued with queue_rcu_work(), so they run only after an RCU grace period,\nonce all readers walking the enabler list have finished. The put must run\nin process context because user_event_put() takes event_mutex on the last\nreference, so a work queue is used rather than call_rcu(). The now-unlocked\nput lets the locked argument of user_event_enabler_destroy() be removed;\nall callers are updated."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"value": "AV:L - The bug is reached only through local syscalls (clone/fork via copy_process and ioctl on tracefs user_events_data); there is no network, adjacent-wireless, or physical-device path into user_event_mm_dup or user_event_enabler_destroy.\nAC:L - A single multithreaded attacker process can register an enabler, then concurrently issue DIAG_IOCSUNREG and fork/clone; the attacker controls both sides of the RCU race, and the fix commit reports reliable KASAN slab-use-after-free reproduction.\nPR:L - Non-persist DIAG_IOCSREG and DIAG_IOCSUNREG enforce no CAP_SYS_ADMIN or perfmon check; only write access to tracefs user_events_data is required, and tracing deployments (Android/Perfetto, ChromeOS, developer tracefs gid mounts) intentionally grant that to unprivileged local users.\nUI:N - The attacker performs registration, concurrent unregistration, and fork entirely within their own process; no victim action, mount, or cooperating user is required beyond running the exploit code.\nS:U - The coupled slab use-after-frees occur in kernel heap during local fork handling and do not cross a VM, IOMMU, or sandbox boundary; impact is standard in-kernel memory corruption on the same host.\nC:H - Fork-time RCU traversal dereferences freed enabler and user_event objects and calls user_event_get on a freed user_event (refcount addition on zero per KASAN), enabling attacker-influenced kernel memory reads via slab grooming.\nI:H - Premature kfree of enabler and user_event while fork duplicates enablement lets an attacker reclaim kmalloc slabs holding tracepoint and trace_event_call state, supporting heap spray and arbitrary kernel write or control-flow hijack primitives.\nA:H - KASAN reports slab-use-after-free in user_event_mm_dup during clone, and repeated concurrent unreg/fork reliably oopses or panics the kernel even before full exploitation, constituting dependable local denial of service."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"kernel/trace/trace_events_user.c"
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],
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"versions": [
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"version": "7235759084a4f8524a46bd2638885ff3b34ce279",
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"lessThan": "25acb6711da6fa0382744fa92bd6d42a22c1ae68",
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"status": "affected",
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"version": "7235759084a4f8524a46bd2638885ff3b34ce279",
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"lessThan": "95400e7039cdfeb0b53652d521d766f1698cae95",
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"status": "affected",
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"version": "7235759084a4f8524a46bd2638885ff3b34ce279",
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"lessThan": "b33ac2d39953efb12f598c0dae242c5f644ea669",
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"kernel/trace/trace_events_user.c"
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],
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"versions": [
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{
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"version": "6.4",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "6.4",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.6.148",
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"lessThanOrEqual": "6.6.*",
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"status": "unaffected",
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},
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{
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"version": "6.12.97",
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"lessThanOrEqual": "6.12.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.18.40",
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"lessThanOrEqual": "6.18.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.1.5",
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"lessThanOrEqual": "7.1.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.2",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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"url": "https://git.kernel.org/stable/c/95400e7039cdfeb0b53652d521d766f1698cae95"
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}
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],
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"title": "tracing/user_events: Fix use-after-free in user_event_mm_dup()",
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