In the Linux kernel, the following vulnerability has been resolved: sched/psi: fix race between file release and pressure write A potential race condition exists between pressure write and cgroup file release regarding the priv member of struct kernfs_open_file, which triggers the uaf reported in [1]. Consider the following scenario involving execution on two separate CPUs: CPU0 CPU1 ==== ==== vfs_rmdir() kernfs_iop_rmdir() cgroup_rmdir() cgroup_kn_lock_live() cgroup_destroy_locked() cgroup_addrm_files() cgroup_rm_file() kernfs_remove_by_name() kernfs_remove_by_name_ns() vfs_write() __kernfs_remove() new_sync_write() kernfs_drain() kernfs_fop_write_iter() kernfs_drain_open_files() cgroup_file_write() kernfs_release_file() pressure_write() cgroup_file_release() ctx = of->priv; kfree(ctx); of->priv = NULL; cgroup_kn_unlock() cgroup_kn_lock_live() cgroup_get(cgrp) cgroup_kn_unlock() if (ctx->psi.trigger) // here, trigger uaf for ctx, that is of->priv The cgroup_rmdir() is protected by the cgroup_mutex, it also safeguards the memory deallocation of of->priv performed within cgroup_file_release(). However, the operations involving of->priv executed within pressure_write() are not entirely covered by the protection of cgroup_mutex. Consequently, if the code in pressure_write(), specifically the section handling the ctx variable executes after cgroup_file_release() has completed, a uaf vulnerability involving of->priv is triggered. Therefore, the issue can be resolved by extending the scope of the cgroup_mutex lock within pressure_write() to encompass all code paths involving of->priv, thereby properly synchronizing the race condition occurring between cgroup_file_release() and pressure_write(). And, if an live kn lock can be successfully acquired while executing the pressure write operation, it indicates that the cgroup deletion process has not yet reached its final stage; consequently, the priv pointer within open_file cannot be NULL. Therefore, the operation to retrieve the ctx value must be moved to a point *after* the live kn lock has been successfully acquired. In another situation, specifically after entering cgroup_kn_lock_live() but before acquiring cgroup_mutex, there exists a different class of race condition: CPU0: write memory.pressure CPU1: write cgroup.pressure=0 =========================== ============================= kernfs_fop_write_iter() kernfs_get_active_of(of) pressure_write() cgroup_kn_lock_live(memory.pressure) cgroup_tryget(cgrp) kernfs_break_active_protection(kn) ... blocks on cgroup_mutex cgroup_pressure_write() cgroup_kn_lock_live(cgroup.pressure) cgroup_file_show(memory.pressure, false) kernfs_show(false) kernfs_drain_open_files() cgroup_file_release(of) kfree(ctx) of->priv = NULL cgroup_kn_unlock() ... acquires cgroup_mutex ctx = of->priv; // may now be NULL if (ctx->psi.trigger) // NULL dereference Consequently, there is a possibility that of->priv is NULL, the pressure write needs to check for this. Now that the scope of the cgroup_mutex has been expanded, the original explicit cgroup_get/put operations are no longer necessary, this is because acquiring/releasing the live kn lock inherently executes a cgroup get/put operation. [1] BUG: KASAN: slab-use-after-free in pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011 Call Trace: pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011 cgroup_file_write+0x36f/0x790 kernel/cgroup/cgroup.c:43 ---truncated---

It is, therefore, affected by a vulnerability as referenced in the ALAS2023-2026-2032 advisory.

    In the Linux kernel, the following vulnerability has been resolved:

    sched/psi: fix race between file release and pressure write (CVE-2026-52991)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-2014 advisory.

    In the Linux kernel, the following vulnerability has been resolved:

    ipv6: use RCU in ip6_output() (CVE-2025-40158)

    In the Linux kernel, the following vulnerability has been resolved:

    gpio: Fix resource leaks on errors in gpiochip_add_data_with_key() (CVE-2026-31732)

    In the Linux kernel, the following vulnerability has been resolved:

    bpf: Reject sleepable kprobe_multi programs at attach time (CVE-2026-43010)

    In the Linux kernel, the following vulnerability has been resolved:

    net: Drop the lock in skb_may_tx_timestamp() (CVE-2026-43216)

    In the Linux kernel, the following vulnerability has been resolved:

    bpf: Fix tcx/netkit detach permissions when prog fd isn't given (CVE-2026-45932)

    In the Linux kernel, the following vulnerability has been resolved:

    ip6_vti: set netns_immutable on the fallback device. (CVE-2026-52909)

    In the Linux kernel, the following vulnerability has been resolved:

    bonding: 3ad: implement proper RCU rules for port->aggregator (CVE-2026-52975)

    In the Linux kernel, the following vulnerability has been resolved:

    sched/psi: fix race between file release and pressure write (CVE-2026-52991)

    In the Linux kernel, the following vulnerability has been resolved:

    sctp: disable BH before calling udp_tunnel_xmit_skb() (CVE-2026-53070)

    In the Linux kernel, the following vulnerability has been resolved:

    fuse: limit FUSE_NOTIFY_RETRIEVE to uptodate folios (CVE-2026-53167)

    In the Linux kernel, the following vulnerability has been resolved:

    fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh() (CVE-2026-53341)

    In the Linux kernel, the following vulnerability has been resolved:

    af_unix: Set gc_in_progress to true in unix_gc(). (CVE-2026-53361)

    In the Linux kernel, the following vulnerability has been resolved:

    virtiofs: fix UAF on submount umount

    iput() called from fuse_release_end() can Oops if the super block hasalready been destroyed.  Normally     this is prevented by waiting fornum_waiting to go down to zero before commencing with super block     shutdown.

    This only works, however, for the last submount instance, as the waitcounter is per connection, not per     superblock.

    Revert to using synchronous release requests for the auto_submounts case,which is virtiofs only at this     time. (CVE-2026-53381)

    In the Linux kernel, the following vulnerability has been resolved:

    vc_screen: fix null-ptr-deref in vcs_notifier() during concurrent vcs_write

    A KASAN null-ptr-deref was observed in vcs_notifier():

    BUG: KASAN: null-ptr-deref in vcs_notifier+0x98/0x130Read of size 2 at addr qmp_cmd_name:
    qmp_capabilities, arguments: {}

    The issue is a race condition in vcs_write(). When the console_lock istemporarily dropped (to copy data     from userspace), the vc_data pointerobtained from vcs_vc() may become stale. After re-acquiring the     lock,vcs_vc() is called again to re-validate the pointer. If the vc has beendeallocated in the meantime,     vcs_vc() returns NULL, and the while loopbreaks (with written > 0). However, after the loop,     vcs_scr_updated(vc)is still called with the now-NULL vc pointer, leading to a null pointerdereference in     the notifier chain (vcs_notifier dereferences param->vc).

    Fix this by adding a NULL check for vc before calling vcs_scr_updated(). (CVE-2026-53385)

    In the Linux kernel, the following vulnerability has been resolved:

    fuse: re-lock request before replacing page cache folio

    fuse_try_move_folio() unlocks the request on entry but does notre-lock it on the success path. This means     fuse_chan_abort() can end therequest and free the fuse_io_args (eg fuse_readpages_end()) while     thesubsequent copy chain logic after fuse_try_move_folio() accesses thefuse_io_args, leading to use-after-     free issues.

    Fix this by calling lock_request() before replace_page_cache_folio().This ensures the request is locked on     the success path which willprevent the fuse_io_args from being freed while the later copying logicruns,     and also ensures that the ap->folios[i]->mapping is never nullsince ap->folios[i] will always point to the     newfolio afterreplace_page_cache_folio(). (CVE-2026-53388)

    In the Linux kernel, the following vulnerability has been resolved:

    NFSv4/pNFS: reject zero-length r_addr in nfs4_decode_mp_ds_addr (CVE-2026-53391)

    In the Linux kernel, the following vulnerability has been resolved:

    nfsd: reset write verifier on deferred writeback errors (CVE-2026-53393)

    In the Linux kernel, the following vulnerability has been resolved:

    nfsd: avoid leaking pre-allocated openowner on unconfirmed retry race (CVE-2026-53394)

    In the Linux kernel, the following vulnerability has been resolved:

    nfsd: fix posix_acl leak on SETACL decode failure (CVE-2026-53397)

    In the Linux kernel, the following vulnerability has been resolved:

    i2c: core: fix adapter registration race

    Adapters can be looked up based on their id using i2c_get_adapter()which takes a reference to the embedded     struct device.

    Make sure that the adapter (including its struct device) has beeninitialised before adding it to the IDR     to avoid accessing uninitialiseddata which could, for example, lead to NULL-pointer dereferences oruse-     after-free.

    Note that the i2c-dev chardev, which is registered from a bus notifier,currently uses i2c_get_adapter() so     the adapter needs to be added to theIDR before registration. (CVE-2026-53400)

    In the Linux kernel, the following vulnerability has been resolved:

    fbdev: Fix fb_new_modelist to prevent null-ptr-deref in fb_videomode_to_var

    info->var, a framebuffer's current mode, is expected to have a matchingentry in info->modelist.
    var_to_display() relies on this and treats afailed fb_match_mode() as This should not happen.
    fb_set_var() keeps ittrue by adding the mode to the list on every change, anddo_register_framebuffer()     does the same at registration.

    store_modes() replaces the modelist from userspace. fb_new_modelist()validates the new modes but does not     check that info->var still has amatch. It relies on fbcon_new_modelist() to re-point consoles, but     thatonly handles consoles mapped to the framebuffer. With fbcon unbound thereare none, so info->var is     left describing a mode that is no longer in thelist.

    A later console takeover runs var_to_display(), where fb_match_mode()returns NULL and leaves     fb_display[i].mode NULL. fbcon_switch() passes itto display_to_var(), and fb_videomode_to_var()     dereferences the NULL mode.

    Keep the current mode in the list in fb_new_modelist(), the same wayfb_set_var() does. (CVE-2026-53403)

    In the Linux kernel, the following vulnerability has been resolved:

    pNFS: Fix use-after-free in pnfs_update_layout() (CVE-2026-63800)

    In the Linux kernel, the following vulnerability has been resolved:

    blk-cgroup: fix UAF in __blkcg_rstat_flush() (CVE-2026-63802)

    In the Linux kernel, the following vulnerability has been resolved:

    KVM: Replace guest-triggerable BUG_ON() in ioeventfd datamatch with get_unaligned() (CVE-2026-63806)

    In the Linux kernel, the following vulnerability has been resolved:

    KVM: x86/mmu: Ensure hugepage is in by slot before checking max mapping level (CVE-2026-63807)

    In the Linux kernel, the following vulnerability has been resolved:

    bpf: use kvfree() for replaced sysctl write buffer (CVE-2026-63809)

    In the Linux kernel, the following vulnerability has been resolved:

    block: Avoid mounting the bdev pseudo-filesystem in userspace (CVE-2026-63810)

    In the Linux kernel, the following vulnerability has been resolved:

    keys: Pin request_key_auth payload in instantiate paths (CVE-2026-63823)

    In the Linux kernel, the following vulnerability has been resolved:

    KEYS: fix overflow in keyctl_pkey_params_get_2() (CVE-2026-63824)

    In the Linux kernel, the following vulnerability has been resolved:

    fbdev: fix use-after-free in store_modes() (CVE-2026-63826)

    In the Linux kernel, the following vulnerability has been resolved:

    net: ip_gre: require CAP_NET_ADMIN in the device netns for changelink (CVE-2026-63829)

    In the Linux kernel, the following vulnerability has been resolved:

    drivers/base/memory: set mem->altmap after successful device registration (CVE-2026-64244)

    In the Linux kernel, the following vulnerability has been resolved:

    fbdev: modedb: fix a possible UAF in fb_find_mode() (CVE-2026-64245)

    In the Linux kernel, the following vulnerability has been resolved:

    kernel/fork: clear PF_BLOCK_TS in copy_process() (CVE-2026-64253)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of kernel installed on the remote host is prior to 5.10.260-259.1061. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2KERNEL-5.10-2026-128 advisory.

    In the Linux kernel, the following vulnerability has been resolved:

    ipv6: use RCU in ip6_output() (CVE-2025-40158)

    In the Linux kernel, the following vulnerability has been resolved:

    xfrm: Wait for RCU readers during policy netns exit (CVE-2026-43091)

    In the Linux kernel, the following vulnerability has been resolved:

    sched/psi: fix race between file release and pressure write (CVE-2026-52991)

    In the Linux kernel, the following vulnerability has been resolved:

    sctp: validate embedded INIT chunk and address list lengths in cookie (CVE-2026-53224)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

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

  - sched/psi: fix race between file release and pressure write A potential race condition exists between     pressure write and cgroup file release regarding the priv member of struct kernfs_open_file, which     triggers the uaf reported in [1]. Consider the following scenario involving execution on two separate     CPUs: CPU0 CPU1 ==== ==== vfs_rmdir() kernfs_iop_rmdir() cgroup_rmdir() cgroup_kn_lock_live()     cgroup_destroy_locked() cgroup_addrm_files() cgroup_rm_file() kernfs_remove_by_name()     kernfs_remove_by_name_ns() vfs_write() __kernfs_remove() new_sync_write() kernfs_drain()     kernfs_fop_write_iter() kernfs_drain_open_files() cgroup_file_write() kernfs_release_file()     pressure_write() cgroup_file_release() ctx = of->priv; kfree(ctx); of->priv = NULL; cgroup_kn_unlock()     cgroup_kn_lock_live() cgroup_get(cgrp) cgroup_kn_unlock() if (ctx->psi.trigger) // here, trigger uaf for     ctx, that is of->priv The cgroup_rmdir() is protected by the cgroup_mutex, it also safeguards the memory     deallocation of of->priv performed within cgroup_file_release(). However, the operations involving     of->priv executed within pressure_write() are not entirely covered by the protection of cgroup_mutex.
    Consequently, if the code in pressure_write(), specifically the section handling the ctx variable executes     after cgroup_file_release() has completed, a uaf vulnerability involving of->priv is triggered. Therefore,     the issue can be resolved by extending the scope of the cgroup_mutex lock within pressure_write() to     encompass all code paths involving of->priv, thereby properly synchronizing the race condition occurring     between cgroup_file_release() and pressure_write(). And, if an live kn lock can be successfully acquired     while executing the pressure write operation, it indicates that the cgroup deletion process has not yet     reached its final stage; consequently, the priv pointer within open_file cannot be NULL. Therefore, the     operation to retrieve the ctx value must be moved to a point *after* the live kn lock has been     successfully acquired. In another situation, specifically after entering cgroup_kn_lock_live() but before     acquiring cgroup_mutex, there exists a different class of race condition: CPU0: write memory.pressure     CPU1: write cgroup.pressure=0 =========================== =============================     kernfs_fop_write_iter() kernfs_get_active_of(of) pressure_write() cgroup_kn_lock_live(memory.pressure)     cgroup_tryget(cgrp) kernfs_break_active_protection(kn) ... blocks on cgroup_mutex cgroup_pressure_write()     cgroup_kn_lock_live(cgroup.pressure) cgroup_file_show(memory.pressure, false) kernfs_show(false)     kernfs_drain_open_files() cgroup_file_release(of) kfree(ctx) of->priv = NULL cgroup_kn_unlock() ...
    acquires cgroup_mutex ctx = of->priv; // may now be NULL if (ctx->psi.trigger) // NULL dereference     Consequently, there is a possibility that of->priv is NULL, the pressure write needs to check for this.
    Now that the scope of the cgroup_mutex has been expanded, the original explicit cgroup_get/put operations     are no longer necessary, this is because acquiring/releasing the live kn lock inherently executes a cgroup     get/put operation. [1] BUG: KASAN: slab-use-after-free in pressure_write+0xa4/0x210     kernel/cgroup/cgroup.c:4011 Call Trace: pressure_write+0xa4/0x210 kernel/cgroup/cgroup.c:4011     cgroup_file_write+0x36f/0x790 kernel/cgroup/cgroup.c:43 ---truncated--- (CVE-2026-52991)

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

ID	Name	Product	Family	Severity
332051	Amazon Linux 2023 : bpftool, kernel, kernel-devel (ALAS2023-2026-2032)	Nessus	Amazon Linux Local Security Checks	high
332042	Amazon Linux 2023 : bpftool6.12, kernel6.12, kernel6.12-devel (ALAS2023-2026-2014)	Nessus	Amazon Linux Local Security Checks	medium
332011	Amazon Linux 2 : kernel, --advisory ALAS2KERNEL-5.10-2026-128 (ALASKERNEL-5.10-2026-128)	Nessus	Amazon Linux Local Security Checks	critical
322714	Linux Distros Unpatched Vulnerability : CVE-2026-52991	Nessus	Misc.	high
322020	Amazon Linux 2023 : bpftool6.18, kernel6.18, kernel6.18-devel (ALAS2023-2026-1866)	Nessus	Amazon Linux Local Security Checks	high

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CVE-2026-52991

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Tenable Plugins

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critical

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