CVE-2026-53262

published 2026-06-25

CVE-2026-53262: In the Linux kernel, the following vulnerability has been resolved: l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl() pppol2tp_ioctl() read…

Priority P3 40 high 7.8 CVSS 3.1

AV L AC L PR L UI N S U C H I H A H

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

l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()

pppol2tp_ioctl() read sock->sk->sk_user_data directly without any
locks or reference counting. If a controllable sleep was induced during
copy_from_user() (e.g. via a userfaultfd page fault sleep), a concurrent
socket close could trigger pppol2tp_session_close() asynchronously. This
frees the l2tp_session structure via the l2tp_session_del_work workqueue.
Upon resuming, the ioctl thread dereferences the stale session pointer,
resulting in a Use-After-Free (UAF).

Fix this by securely fetching the session reference using the RCU-safe,
refcounted helper pppol2tp_sock_to_session(sk) on entry. This locks the
session's refcount across the sleep. We structured the function to exit
via standard err breaks, guaranteeing that l2tp_session_put() is cleanly
called on all return paths to drop the reference.

To preserve existing behavior we validate the session and its magic
signature only for the specific L2TP commands that require it. This
ensures that generic/unknown ioctls called on an unconnected socket
still return -ENOIOCTLCMD and correctly fall back to generic handlers
(e.g. in sock_do_ioctl()).

Affected

14 ranges

Vendor	Product	Version range	Fixed in
linux	linux	—	—
linux	linux	>= fd558d186df2c13a22455373858bae634a4795af < 78cdfdca88cbf731a92f3b9ee5427c633dd94e28	78cdfdca88cbf731a92f3b9ee5427c633dd94e28
linux	linux	>= fd558d186df2c13a22455373858bae634a4795af < e251d4cdfc725c9e7d686161e3b775a0e7d95053	e251d4cdfc725c9e7d686161e3b775a0e7d95053
linux	linux	>= fd558d186df2c13a22455373858bae634a4795af < 62f327e287cf7b595ae3f73ba72f5cd2a9e9f39f	62f327e287cf7b595ae3f73ba72f5cd2a9e9f39f
linux	linux	>= fd558d186df2c13a22455373858bae634a4795af < a213a8950414c684999dcf03edeea6c46ede172e	a213a8950414c684999dcf03edeea6c46ede172e
linux	linux_kernel	—	—
linux	linux_kernel	—	—
linux	linux_kernel	—	—
linux	linux_kernel	—	—
linux	linux_kernel	—	—
linux	linux_kernel	—	—
linux	linux_kernel	>= 2.6.35 < 6.12.94	6.12.94
linux	linux_kernel	>= 6.13 < 6.18.36	6.18.36
linux	linux_kernel	>= 6.19 < 7.0.13	7.0.13

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