CVE-2026-72071 (GCVE-0-2026-72071)
Vulnerability from cvelistv5
Published
2026-08-15 05:52
Modified
2026-08-17 05:40
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
tracing/user_events: Fix use-after-free in user_event_mm_dup()
user_event_mm_dup() walks the parent mm's enabler list locklessly under
rcu_read_lock() during fork() (from copy_process()); it does not take
event_mutex:
rcu_read_lock();
list_for_each_entry_rcu(enabler, &old_mm->enablers, mm_enablers_link)
enabler->event = user_event_get(orig->event);
user_event_enabler_destroy() removes an enabler from that list with
list_del_rcu() and then, without waiting for a grace period, drops the
enabler's user_event reference with user_event_put() and frees the enabler
with kfree(). A reader that loaded the enabler before the list_del_rcu()
can still be walking it, which leads to two use-after-frees:
- kfree(enabler) frees the enabler while that reader dereferences
enabler->event.
- user_event_put() may drop the last reference to the user_event, which
is then freed (via delayed_destroy_user_event() on a work queue), while
the same reader does user_event_get(orig->event) on it.
Both are reachable by an unprivileged task that can open user_events_data:
one multithreaded process that registers an enabler and then concurrently
unregisters it and calls fork() triggers the race. KASAN reports a
slab-use-after-free in user_event_mm_dup() during clone(), with a
"refcount_t: addition on 0" warning when the user_event is freed.
The enabler use-after-free was found first; the user_event one was reported
by XIAO WU, and the earlier enabler-only fix did not address it.
Defer both the user_event_put() and the kfree(enabler) to a work item
queued with queue_rcu_work(), so they run only after an RCU grace period,
once all readers walking the enabler list have finished. The put must run
in process context because user_event_put() takes event_mutex on the last
reference, so a work queue is used rather than call_rcu(). The now-unlocked
put lets the locked argument of user_event_enabler_destroy() be removed;
all callers are updated.
References
Impacted products
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"kernel/trace/trace_events_user.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
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"version": "7235759084a4f8524a46bd2638885ff3b34ce279",
"versionType": "git"
},
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"version": "7235759084a4f8524a46bd2638885ff3b34ce279",
"versionType": "git"
},
{
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"status": "affected",
"version": "7235759084a4f8524a46bd2638885ff3b34ce279",
"versionType": "git"
},
{
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"status": "affected",
"version": "7235759084a4f8524a46bd2638885ff3b34ce279",
"versionType": "git"
},
{
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"version": "7235759084a4f8524a46bd2638885ff3b34ce279",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"kernel/trace/trace_events_user.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "6.4"
},
{
"lessThan": "6.4",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.148",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.97",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.40",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.5",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.148",
"versionStartIncluding": "6.4",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.97",
"versionStartIncluding": "6.4",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.5",
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2",
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"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"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\u0027s 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, \u0026old_mm-\u003eenablers, mm_enablers_link)\n\t\tenabler-\u003eevent = user_event_get(orig-\u003eevent);\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\u0027s 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-\u003eevent.\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-\u003eevent) 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."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"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."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-17T05:40:01.974Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/25acb6711da6fa0382744fa92bd6d42a22c1ae68"
},
{
"url": "https://git.kernel.org/stable/c/95400e7039cdfeb0b53652d521d766f1698cae95"
},
{
"url": "https://git.kernel.org/stable/c/b33ac2d39953efb12f598c0dae242c5f644ea669"
},
{
"url": "https://git.kernel.org/stable/c/05b24f68f78ff3a1ef7f015f7327b35886b741f6"
},
{
"url": "https://git.kernel.org/stable/c/50fd6dd755c6e48a38af2fa4621167eea56829c2"
}
],
"title": "tracing/user_events: Fix use-after-free in user_event_mm_dup()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-72071",
"datePublished": "2026-08-15T05:52:23.215Z",
"dateReserved": "2026-08-09T03:40:39.904Z",
"dateUpdated": "2026-08-17T05:40:01.974Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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