In the Linux kernel, the following vulnerability has been resolved: exit: hold a reference to thread_pid across proc_flush_pid Commit 0a36bad01731 ("release_task: kill the no longer needed get/put_pid(thread_pid)") removed the reference around proc_flush_pid(). It assumed that free_pids(post.pids) at the end of release_task() would keep thread_pid alive until then. That assumption is wrong. __change_pid() only records a detached PID in post.pids when pid_has_task() is false for every PIDTYPE. If another task still uses the exiting task's PID as its process group or session ID, __unhash_process() removes the exiting task's PIDTYPE_PID link but leaves the PID out of post.pids. release_task() therefore holds no reference to it after dropping tasklist_lock. The other task can then remove the remaining PIDTYPE links. Its free_pids() call schedules delayed_put_pid(), and the RCU callback can free the PID before the first release_task() reaches proc_flush_pid(). An unprivileged reproducer races wait4(-1) against setsid() to trigger this ordering. Three of three fresh v7.2 KASAN boots reported: BUG: KASAN: slab-use-after-free in proc_invalidate_siblings_dcache+0x3e2/0x3f0 Read of size 8 by task h7_pid_reaper/1921 Call Trace: proc_invalidate_siblings_dcache release_task wait_consider_task __do_wait do_wait kernel_wait4 Freed by task 0: kmem_cache_free put_pid delayed_put_pid rcu_core Last potentially related work creation: __call_rcu_common free_pids ksys_setsid KASAN identified a 144-byte object from the pid cache and located the bad read 80 bytes into the freed object, matching pid->inodes. With an explicit reference, three of three fresh boots completed without a KASAN report. The concurrent RCU callback dropped its reference while proc_flush_pid() was protected, and the balancing put_pid() performed the final free afterward. Take a reference before __unhash_process() clears p->thread_pid and release it after proc_flush_pid() completes. A tested source reproducer is available privately on request. No controlled read or write, information leak, or privilege escalation is claimed. The mainline patch applies directly to v6.19.y and newer; v6.16.y through v6.18.y need a context-adjusted backport.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - In the Linux kernel, the following vulnerability has been resolved: exit: hold a reference to thread_pid
    across proc_flush_pid Commit 0a36bad01731 ("release_task: kill the no longer needed
    get/put_pid(thread_pid)") removed the reference around proc_flush_pid(). It assumed that
    free_pids(post.pids) at the end of release_task() would keep thread_pid alive until then. That assumption
    is wrong. __change_pid() only records a detached PID in post.pids when pid_has_task() is false for every
    PIDTYPE. If another task still uses the exiting task's PID as its process group or session ID,
    __unhash_process() removes the exiting task's PIDTYPE_PID link but leaves the PID out of post.pids.
    release_task() therefore holds no reference to it after dropping tasklist_lock. The other task can then
    remove the remaining PIDTYPE links. Its free_pids() call schedules delayed_put_pid(), and the RCU callback
    can free the PID before the first release_task() reaches proc_flush_pid(). An unprivileged reproducer
    races wait4(-1) against setsid() to trigger this ordering. Three of three fresh v7.2 KASAN boots reported:
    BUG: KASAN: slab-use-after-free in proc_invalidate_siblings_dcache+0x3e2/0x3f0 Read of size 8 by task
    h7_pid_reaper/1921 Call Trace: proc_invalidate_siblings_dcache release_task wait_consider_task __do_wait
    do_wait kernel_wait4 Freed by task 0: kmem_cache_free put_pid delayed_put_pid rcu_core Last potentially
    related work creation: __call_rcu_common free_pids ksys_setsid KASAN identified a 144-byte object from the
    pid cache and located the bad read 80 bytes into the freed object, matching pid->inodes. With an explicit
    reference, three of three fresh boots completed without a KASAN report. The concurrent RCU callback
    dropped its reference while proc_flush_pid() was protected, and the balancing put_pid() performed the
    final free afterward. Take a reference before __unhash_process() clears p->thread_pid and release it after
    proc_flush_pid() completes. A tested source reproducer is available privately on request. No controlled
    read or write, information leak, or privilege escalation is claimed. The mainline patch applies directly
    to v6.19.y and newer; v6.16.y through v6.18.y need a context-adjusted backport. (CVE-2026-97903)

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - exit: hold a reference to thread_pid across proc_flush_pid Commit 0a36bad01731 (release_task: kill the no     longer needed get/put_pid(thread_pid)) removed the reference around proc_flush_pid(). It assumed that     free_pids(post.pids) at the end of release_task() would keep thread_pid alive until then. That assumption     is wrong. __change_pid() only records a detached PID in post.pids when pid_has_task() is false for every     PIDTYPE. If another task still uses the exiting task's PID as its process group or session ID,
    __unhash_process() removes the exiting task's PIDTYPE_PID link but leaves the PID out of post.pids.
    release_task() therefore holds no reference to it after dropping tasklist_lock. The other task can then     remove the remaining PIDTYPE links. Its free_pids() call schedules delayed_put_pid(), and the RCU callback     can free the PID before the first release_task() reaches proc_flush_pid(). An unprivileged reproducer     races wait4(-1) against setsid() to trigger this ordering. Three of three fresh v7.2 KASAN boots reported:
    BUG: KASAN: slab-use-after-free in proc_invalidate_siblings_dcache+0x3e2/0x3f0 Read of size 8 by task     h7_pid_reaper/1921 Call Trace: proc_invalidate_siblings_dcache release_task wait_consider_task __do_wait     do_wait kernel_wait4 Freed by task 0: kmem_cache_free put_pid delayed_put_pid rcu_core Last potentially     related work creation: __call_rcu_common free_pids ksys_setsid KASAN identified a 144-byte object from the     pid cache and located the bad read 80 bytes into the freed object, matching pid->inodes. With an explicit     reference, three of three fresh boots completed without a KASAN report. The concurrent RCU callback     dropped its reference while proc_flush_pid() was protected, and the balancing put_pid() performed the     final free afterward. Take a reference before __unhash_process() clears p->thread_pid and release it after     proc_flush_pid() completes. A tested source reproducer is available privately on request. No controlled     read or write, information leak, or privilege escalation is claimed. The mainline patch applies directly     to v6.19.y and newer; v6.16.y through v6.18.y need a context-adjusted backport. (CVE-2026-97903)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
475134	Google: sys-kernel/cchost-kernel-6_18, sys-kernel/csql-kernel-6_18, sys-kernel/lakitu-kernel-6_18, sys-kernel/lakitu-nc-kernel-6_18: security update to 19999.44.106	Tenable Cloud Security	Google COS Security Checks	Local	high
475134	Google: sys-kernel/cchost-kernel-6_18, sys-kernel/csql-kernel-6_18, sys-kernel/lakitu-kernel-6_18, sys-kernel/lakitu-nc-kernel-6_18: security update to 19999.44.106	Tenable Self-Hosted Container Security	Google COS Security Checks	Local	high
350434	Linux Distros Unpatched Vulnerability : CVE-2026-97903	Nessus	Misc.	Local	high

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CVE-2026-97903

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