In the Linux kernel, the following vulnerability has been resolved: l2tp: use list_del_rcu in l2tp_session_unhash An unprivileged local user can pin a host CPU indefinitely in l2tp_session_get_by_ifname() by issuing L2TP_CMD_SESSION_GET on L2TP_ATTR_IFNAME concurrently with L2TP_CMD_SESSION_CREATE and L2TP_CMD_SESSION_DELETE on the same tunnel. All three commands take GENL_UNS_ADMIN_PERM, so CAP_NET_ADMIN in the netns user namespace suffices; on any host that has l2tp_core loaded the trigger is reachable from a standard `unshare -Urn` sandbox. l2tp_session_unhash() removes a session from tunnel->session_list with list_del_init(), but that list is walked by l2tp_session_get_by_ifname() with list_for_each_entry_rcu() under rcu_read_lock_bh(). list_del_init() leaves the deleted entry's next/prev self-pointing; a reader that has loaded the entry and then advances pos->list.next reads &session->list, container_of()s back to the same session, and list_for_each_entry_rcu() never reaches the list head. The CPU stays in strcmp() inside the walker, with BH and preemption disabled, so RCU grace periods on the host stall behind it and the wedged thread cannot be killed (SIGKILL is delivered on syscall return). Use list_del_rcu() to match the existing list_add_rcu() in l2tp_session_register(); the deleted session remains visible to in-flight walkers with consistent next/prev pointers until kfree_rcu() in l2tp_session_free() releases it. tunnel->session_list has exactly one list_del_init() call site; the list_del_init (&session->clist) at l2tp_core.c:533 operates on the per-collision list, which is not walked under RCU. list_empty(&session->list) is not used anywhere in net/l2tp/ after the unhash point, so dropping the post-delete self-init is safe; the fix has no userspace-visible behavior change.

An update of the linux package has been released.

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

  - In the Linux kernel, the following vulnerability has been resolved: l2tp: use list_del_rcu in     l2tp_session_unhash An unprivileged local user can pin a host CPU indefinitely in     l2tp_session_get_by_ifname() by issuing L2TP_CMD_SESSION_GET on L2TP_ATTR_IFNAME concurrently with     L2TP_CMD_SESSION_CREATE and L2TP_CMD_SESSION_DELETE on the same tunnel. All three commands take     GENL_UNS_ADMIN_PERM, so CAP_NET_ADMIN in the netns user namespace suffices; on any host that has l2tp_core     loaded the trigger is reachable from a standard `unshare -Urn` sandbox. l2tp_session_unhash() removes a     session from tunnel->session_list with list_del_init(), but that list is walked by     l2tp_session_get_by_ifname() with list_for_each_entry_rcu() under rcu_read_lock_bh(). list_del_init()     leaves the deleted entry's next/prev self-pointing; a reader that has loaded the entry and then advances     pos->list.next reads &session->list, container_of()s back to the same session, and     list_for_each_entry_rcu() never reaches the list head. The CPU stays in strcmp() inside the walker, with     BH and preemption disabled, so RCU grace periods on the host stall behind it and the wedged thread cannot     be killed (SIGKILL is delivered on syscall return). Use list_del_rcu() to match the existing     list_add_rcu() in l2tp_session_register(); the deleted session remains visible to in-flight walkers with     consistent next/prev pointers until kfree_rcu() in l2tp_session_free() releases it. tunnel->session_list     has exactly one list_del_init() call site; the list_del_init (&session->clist) at l2tp_core.c:533 operates     on the per-collision list, which is not walked under RCU. list_empty(&session->list) is not used anywhere     in net/l2tp/ after the unhash point, so dropping the post-delete self-init is safe; the fix has no     userspace-visible behavior change. (CVE-2026-64119)

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

ID	Name	Product	Family	Type	Severity
340681	Ubuntu 24.04 LTS / 26.04 LTS / Pro Realtime 24.04 LTS : Linux kernel (NVIDIA) vulnerabilities (USN-8663-1)	Nessus	Ubuntu Local Security Checks	Local	high
340045	Ubuntu 26.04 LTS : Linux kernel (NVIDIA BaseOS) vulnerabilities (USN-8664-1)	Nessus	Ubuntu Local Security Checks	Local	high
333944	Photon OS 5.0: Linux PHSA-2026-5.0-92-0864	Nessus	PhotonOS Local Security Checks	Local	high
327977	Linux Distros Unpatched Vulnerability : CVE-2026-64119	Nessus	Misc.	Local	medium
318773	Photon OS 5.0: Linux PHSA-2026-5.0-0864	Nessus	PhotonOS Local Security Checks	Local	high

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