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

Vulnerability from cvelistv5 – Published: 2026-06-25 08:39 – Updated: 2026-08-05 12:34
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
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: fd558d186df2c13a22455373858bae634a4795af , < 78cdfdca88cbf731a92f3b9ee5427c633dd94e28 (git)
Affected: fd558d186df2c13a22455373858bae634a4795af , < e251d4cdfc725c9e7d686161e3b775a0e7d95053 (git)
Affected: fd558d186df2c13a22455373858bae634a4795af , < 62f327e287cf7b595ae3f73ba72f5cd2a9e9f39f (git)
Affected: fd558d186df2c13a22455373858bae634a4795af , < a213a8950414c684999dcf03edeea6c46ede172e (git)
guessed Create a notification for this product.
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)
guessed Create a notification for this product.
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          "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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            "version": "3.1"
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    "redhat_vex": {
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      "cve": "CVE-2026-53262",
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      "source": "Red Hat CSAF VEX",
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      "title": "kernel: l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()",
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      "cve": "CVE-2026-53262",
      "id": "CVE-2026-53262",
      "initial_release_date": "2026-06-26T02:08:14Z",
      "product_status:first_fixed": "2",
      "product_status:known_affected": "648",
      "product_status:recommended": "304",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-53262",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-53262.json",
      "version": "17"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


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