CVE-2026-53262 (GCVE-0-2026-53262)

Vulnerability from cvelistv5 – Published: 2026-06-25 08:39 – Updated: 2026-06-25 08:39
VLAI
Title
l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()
Summary
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()).
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: fd558d186df2c13a22455373858bae634a4795af , < 78cdfdca88cbf731a92f3b9ee5427c633dd94e28 (git)
Affected: fd558d186df2c13a22455373858bae634a4795af , < e251d4cdfc725c9e7d686161e3b775a0e7d95053 (git)
Affected: fd558d186df2c13a22455373858bae634a4795af , < 62f327e287cf7b595ae3f73ba72f5cd2a9e9f39f (git)
Affected: fd558d186df2c13a22455373858bae634a4795af , < a213a8950414c684999dcf03edeea6c46ede172e (git)
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Linux Linux Affected: 2.6.35
Unaffected: 0 , < 2.6.35 (semver)
Unaffected: 6.12.94 , ≤ 6.12.* (semver)
Unaffected: 6.18.36 , ≤ 6.18.* (semver)
Unaffected: 7.0.13 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nl2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()\n\npppol2tp_ioctl() read sock-\u003esk-\u003esk_user_data directly without any\nlocks or reference counting.  If a controllable sleep was induced during\ncopy_from_user() (e.g. via a userfaultfd page fault sleep), a concurrent\nsocket close could trigger pppol2tp_session_close() asynchronously.  This\nfrees the l2tp_session structure via the l2tp_session_del_work workqueue.\nUpon resuming, the ioctl thread dereferences the stale session pointer,\nresulting in a Use-After-Free (UAF).\n\nFix this by securely fetching the session reference using the RCU-safe,\nrefcounted helper pppol2tp_sock_to_session(sk) on entry.  This locks the\nsession\u0027s refcount across the sleep.  We structured the function to exit\nvia standard err breaks, guaranteeing that l2tp_session_put() is cleanly\ncalled on all return paths to drop the reference.\n\nTo preserve existing behavior we validate the session and its magic\nsignature only for the specific L2TP commands that require it.  This\nensures that generic/unknown ioctls called on an unconnected socket\nstill return -ENOIOCTLCMD and correctly fall back to generic handlers\n(e.g. in sock_do_ioctl())."
        }
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        "dateUpdated": "2026-06-25T08:39:50.550Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/a213a8950414c684999dcf03edeea6c46ede172e"
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      ],
      "title": "l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()",
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    "datePublished": "2026-06-25T08:39:50.550Z",
    "dateReserved": "2026-06-09T07:44:35.394Z",
    "dateUpdated": "2026-06-25T08:39:50.550Z",
    "state": "PUBLISHED"
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      "date": "2026-06-27",
      "epss": "0.00163",
      "percentile": "0.05891"
    }
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}


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