In the Linux kernel, the following vulnerability has been resolved: ksmbd: reject non-VALID session in compound request branch smb2_check_user_session() takes a shortcut for any operation that is not the first in a COMPOUND request: it reuses work->sess (the session bound by the first operation) and validates only the SessionId, then returns "valid". It never re-checks work->sess->state == SMB2_SESSION_VALID, and a SessionId of 0xFFFFFFFFFFFFFFFF (ULLONG_MAX, the MS-SMB2 related-operation value) skips even the id comparison. The standalone path (ksmbd_session_lookup_all() plus the SESSION_SETUP state machine) does enforce the VALID state; the compound branch bypasses all of it. A SESSION_SETUP carrying only an NTLM Type-1 (NtLmNegotiate) blob publishes a fresh SMB2_SESSION_IN_PROGRESS session whose sess->user is still NULL (->user is assigned later, by ntlm_authenticate()). Used as operation 1 of a COMPOUND with operation 2 = TREE_CONNECT (related, SessionId=ULLONG_MAX, \\host\IPC$), the tree-connect then runs on that IN_PROGRESS session and reaches ksmbd_ipc_tree_connect_request(), which dereferences user_name(sess->user) with sess->user == NULL (transport_ipc.c:687/701/704) -> remote NULL-pointer dereference and a kernel Oops that wedges the ksmbd worker for all clients. Reject any non-first compound operation that lands on a session which is not SMB2_SESSION_VALID, mirroring the validity the standalone lookup path enforces. SESSION_SETUP itself legitimately runs on an IN_PROGRESS session, but it is never carried as a non-first compound operation, so multi-leg authentication is unaffected by this check.

An update of the linux package has been released.

The remote Debian 11 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-4700 advisory.

    -------------------------------------------------------------------------     Debian LTS Advisory DLA-4700-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                        Ben Hutchings     July 26, 2026                                 https://wiki.debian.org/LTS
    -------------------------------------------------------------------------

    Package        : linux-6.1     Version        : 6.1.177-1~deb11u1     CVE ID         : CVE-2025-23131 CVE-2026-23272 CVE-2026-23278 CVE-2026-23302                      CVE-2026-31451 CVE-2026-46252 CVE-2026-52928 CVE-2026-53138                      CVE-2026-53139 CVE-2026-53157 CVE-2026-53158 CVE-2026-53163                      CVE-2026-53167 CVE-2026-53325 CVE-2026-53327 CVE-2026-53359                      CVE-2026-53362 CVE-2026-53366 CVE-2026-53381 CVE-2026-53382                      CVE-2026-53383 CVE-2026-53384 CVE-2026-53385 CVE-2026-53388                      CVE-2026-53390 CVE-2026-53391 CVE-2026-53397 CVE-2026-53398                      CVE-2026-53403 CVE-2026-63794 CVE-2026-63795 CVE-2026-63796                      CVE-2026-63798 CVE-2026-63800 CVE-2026-63801 CVE-2026-63803                      CVE-2026-63807 CVE-2026-63808 CVE-2026-63809 CVE-2026-63814                      CVE-2026-63817 CVE-2026-63822 CVE-2026-63823 CVE-2026-63824                      CVE-2026-63827 CVE-2026-63828 CVE-2026-63830 CVE-2026-63831                      CVE-2026-63833 CVE-2026-63834 CVE-2026-63835 CVE-2026-63836                      CVE-2026-64188 CVE-2026-64191 CVE-2026-64246 CVE-2026-64249                      CVE-2026-64252 CVE-2026-64254 CVE-2026-64529     Debian Bug     : 1130365

    Several vulnerabilities have been discovered in the Linux kernel that     may lead to a privilege escalation, denial of service or information     leaks.

    For Debian 11 bullseye, these problems have been fixed in version     6.1.177-1~deb11u1.  This version additionally updates the Microsoft     Azure Network Adapter (mana) driver, and includes many more bug fixes     from stable update 6.1.177.

    We recommend that you upgrade your linux-6.1 packages.

    For the detailed security status of linux-6.1 please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/linux-6.1

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS     Attachment:
    signature.asc     Description: PGP signature

Tenable has extracted the preceding description block directly from the Debian 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.

  - ksmbd: reject non-VALID session in compound request branch smb2_check_user_session() takes a shortcut for     any operation that is not the first in a COMPOUND request: it reuses work->sess (the session bound by the     first operation) and validates only the SessionId, then returns valid. It never re-checks     work->sess->state == SMB2_SESSION_VALID, and a SessionId of 0xFFFFFFFFFFFFFFFF (ULLONG_MAX, the MS-SMB2     related-operation value) skips even the id comparison. The standalone path (ksmbd_session_lookup_all()     plus the SESSION_SETUP state machine) does enforce the VALID state; the compound branch bypasses all of     it. A SESSION_SETUP carrying only an NTLM Type-1 (NtLmNegotiate) blob publishes a fresh     SMB2_SESSION_IN_PROGRESS session whose sess->user is still NULL (->user is assigned later, by     ntlm_authenticate()). Used as operation 1 of a COMPOUND with operation 2 = TREE_CONNECT (related,     SessionId=ULLONG_MAX, \\host\IPC$), the tree-connect then runs on that IN_PROGRESS session and reaches     ksmbd_ipc_tree_connect_request(), which dereferences user_name(sess->user) with sess->user == NULL     (transport_ipc.c:687/701/704) -> remote NULL-pointer dereference and a kernel Oops that wedges the ksmbd     worker for all clients. Reject any non-first compound operation that lands on a session which is not     SMB2_SESSION_VALID, mirroring the validity the standalone lookup path enforces. SESSION_SETUP itself     legitimately runs on an IN_PROGRESS session, but it is never carried as a non-first compound operation, so     multi-leg authentication is unaffected by this check. (CVE-2026-53383)

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

ID	Name	Product	Family	Type	Severity
333954	Photon OS 5.0: Linux PHSA-2026-5.0-92-0916	Nessus	PhotonOS Local Security Checks	Local	high
333941	Photon OS 5.0: Linux PHSA-2026-5.0-92-0926	Nessus	PhotonOS Local Security Checks	Local	high
330014	Debian dla-4700 : linux-config-6.1 - security update	Nessus	Debian Local Security Checks	Local	high
329326	Photon OS 5.0: Linux PHSA-2026-5.0-0926	Nessus	PhotonOS Local Security Checks	Local	high
328058	Linux Distros Unpatched Vulnerability : CVE-2026-53383	Nessus	Misc.	Local	high
326038	Photon OS 5.0: Linux PHSA-2026-5.0-0916	Nessus	PhotonOS Local Security Checks	Local	high

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