CVE-2026-99218 (GCVE-0-2026-99218)

Vulnerability from cvelistv5 – Published: 2026-11-02 16:06 – Updated: 2026-11-03 19:12
VLAI
Title
coredump: hold RCU while releasing parked threads
Summary
In the Linux kernel, the following vulnerability has been resolved: coredump: hold RCU while releasing parked threads coredump_finish() releases the parked threads by clearing ->task in their core_thread entry and calling wake_up_process() on each of them. It does that without holding a reference on the task and without being inside rcu. But calling wake_up_process(task) without rcu here isn't safe. A parked thread doesn't need that wakeup to leave. A spurious wakeup or a preemption after the store is enough for the task to go away. So if the coredump client is preempted between the store and wake_up_process() the thread can exit and be freed in the meantime and try_to_wake_up() takes pi_lock in freed memory. Hold rcu across the loop.
Severity
7 (High)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6847 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: a94e2d408eaedbd85aae259621d46fafc10479a2 , < fd0fbe84312fda2fc187428c92c50b7d03a9d24c (git)
Affected: a94e2d408eaedbd85aae259621d46fafc10479a2 , < 71146c437bae59e5280f657965dc6d006ee3989b (git)
Affected: a94e2d408eaedbd85aae259621d46fafc10479a2 , < 0fce73efee40c65ce26641c5d93942462f9e8307 (git)
Affected: a94e2d408eaedbd85aae259621d46fafc10479a2 , < 16e94ed90b1b02398e044d41fd1db34828daa08e (git)
Affected: a94e2d408eaedbd85aae259621d46fafc10479a2 , < a0f09ff4c6b93312e565cfe75d76c3a551a3ec4c (git)
Affected: a94e2d408eaedbd85aae259621d46fafc10479a2 , < b0eca0edddf4c1dbaf6d1f6a8636b4235f5bc573 (git)
Affected: a94e2d408eaedbd85aae259621d46fafc10479a2 , < 61d58591aa0188bf2463e263962256316ff8b576 (git)
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Linux Linux Affected: 2.6.27
Unaffected: 0 , < 2.6.27 (semver)
Unaffected: 6.1.191 , ≤ 6.1.* (semver)
Unaffected: 6.6.161 , ≤ 6.6.* (semver)
Unaffected: 6.12.115 , ≤ 6.12.* (semver)
Unaffected: 6.18.60 , ≤ 6.18.* (semver)
Unaffected: 7.2.14 , ≤ 7.2.* (semver)
Unaffected: 7.3.1 , ≤ 7.3.* (semver)
Unaffected: 7.4-rc1 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncoredump: hold RCU while releasing parked threads\n\ncoredump_finish() releases the parked threads by clearing -\u003etask in\ntheir core_thread entry and calling wake_up_process() on each of them.\nIt does that without holding a reference on the task and without being\ninside rcu.\n\nBut calling wake_up_process(task) without rcu here isn\u0027t safe. A parked\nthread doesn\u0027t need that wakeup to leave. A spurious wakeup or a\npreemption after the store is enough for the task to go away.\n\nSo if the coredump client is preempted between the store and\nwake_up_process() the thread can exit and be freed in the meantime and\ntry_to_wake_up() takes pi_lock in freed memory.\n\nHold rcu across the loop."
        }
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              "value": "AV:L - The UAF is in coredump_finish(), reached when a local dump signal is delivered via get_signal() -\u003e vfs_coredump() -\u003e do_coredump()/coredump_cleanup(). abort(), a user page-fault SIGSEGV, or tgkill() on the attacker\u0027s own thread group starts that path; no remote protocol supplies the curr-\u003etask pointer later handed to wake_up_process().\nAC:H - coredump_wait() parks siblings in coredump_task_exit() in TASK_IDLE (no TASK_WAKEKILL), so kill/tgkill cannot wake them. The UAF needs the dumper preempted between curr-\u003etask=NULL and wake_up_process() long enough for a spurious or freezer wakeup, full do_exit(), and an RCU GP via delayed_put_task_struct() \u2014 timing the attacker cannot force.\nPR:L - get_signal() dumps the caller\u0027s own dumpable thread group with no capability check. An ordinary user pthread_create()s a sibling and abort()s or faults into vfs_coredump(); coredump_skip() only bails on TASK_DUMPABLE_OFF, which a normal user process is not.\nUI:N - The attacker creates the extra thread and delivers the dump signal inside their own process; no other user must mount media, open a file, or otherwise act.\nS:U - try_to_wake_up() on the freed task_struct corrupts host kernel scheduler state inside the same kernel; this is ordinary in-kernel UAF impact, not a VM, IOMMU, or sandbox escape.\nC:H - wake_up_process() -\u003e try_to_wake_up() reads __state, on_rq, and sched_class from the task_struct after delayed_put_task_struct() has freed it; a sprayable slab UAF read is High confidentiality per UAF guidance.\nI:H - try_to_wake_up() takes raw_spin_lock on the freed p-\u003epi_lock, writes __state, and calls p-\u003esched_class-\u003eenqueue_task(); reclaiming the task_struct slab yields a write and control-flow primitive.\nA:H - Taking pi_lock in memory already freed by delayed_put_task_struct(), as the fix describes, oopses or panics even without a successful spray, so availability is High."
            }
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncoredump: hold RCU while releasing parked threads\n\ncoredump_finish() releases the parked threads by clearing -\u003etask in\ntheir core_thread entry and calling wake_up_process() on each of them.\nIt does that without holding a reference on the task and without being\ninside rcu.\n\nBut calling wake_up_process(task) without rcu here isn\u0027t safe. A parked\nthread doesn\u0027t need that wakeup to leave. A spurious wakeup or a\npreemption after the store is enough for the task to go away.\n\nSo if the coredump client is preempted between the store and\nwake_up_process() the thread can exit and be freed in the meantime and\ntry_to_wake_up() takes pi_lock in freed memory.\n\nHold rcu across the loop."
          }
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        "lastModified": "2026-11-02T16:17:45.740",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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}



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