l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()
CVE-2026-53262 · published 25 Jun 2026
How serious is it
- Severity: high, CVSS score 7.8 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-53262?
Paste this prompt into Claude Code, Cursor or any AI coding tool: it runs a free Shippable scan of your project and fixes what it finds. Built with Lovable, Bolt or v0? Scan your live app. Or upload your package file.
Who is affected
- Linux Linux: fd558d186df2c13a22455373858bae634a4795af to < 312ecea13b67797747eb9d4b9dab8d3846de6dfb, fd558d186df2c13a22455373858bae634a4795af to < 78cdfdca88cbf731a92f3b9ee5427c633dd94e28, fd558d186df2c13a22455373858bae634a4795af to < e251d4cdfc725c9e7d686161e3b775a0e7d95053, fd558d186df2c13a22455373858bae634a4795af to < 62f327e287cf7b595ae3f73ba72f5cd2a9e9f39f
- Linux Linux: 2.6.35
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
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()).
Check your whole app
Dependencies are only half of it. Free and read-only: before you push, run npx shippable-dev scan localhost:3000 in your project folder, no account needed. For your live app, you prove it's yours with a one-line tag first.
References
- git.kernel.org/stable/c/312ecea13b67797747eb9d4b9dab8d3846de6dfb
- git.kernel.org/stable/c/78cdfdca88cbf731a92f3b9ee5427c633dd94e28
- git.kernel.org/stable/c/e251d4cdfc725c9e7d686161e3b775a0e7d95053
- git.kernel.org/stable/c/62f327e287cf7b595ae3f73ba72f5cd2a9e9f39f
- git.kernel.org/stable/c/a213a8950414c684999dcf03edeea6c46ede172e
Merged from CVE List. Last updated 25 Oct 2026. All vulnerabilities · RSS · JSON