CVE-2026-64119

/// Technical description

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 th

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References