CVE-2026-53262 (GCVE-0-2026-53262)
Vulnerability from cvelistv5
Published
2026-06-25 08:39
Modified
2026-08-05 12:34
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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()).
References
Impacted products
Vendor Product Version
Linux Linux Version: fd558d186df2c13a22455373858bae634a4795af
Version: fd558d186df2c13a22455373858bae634a4795af
Version: fd558d186df2c13a22455373858bae634a4795af
Version: fd558d186df2c13a22455373858bae634a4795af
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/l2tp/l2tp_ppp.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "78cdfdca88cbf731a92f3b9ee5427c633dd94e28",
              "status": "affected",
              "version": "fd558d186df2c13a22455373858bae634a4795af",
              "versionType": "git"
            },
            {
              "lessThan": "e251d4cdfc725c9e7d686161e3b775a0e7d95053",
              "status": "affected",
              "version": "fd558d186df2c13a22455373858bae634a4795af",
              "versionType": "git"
            },
            {
              "lessThan": "62f327e287cf7b595ae3f73ba72f5cd2a9e9f39f",
              "status": "affected",
              "version": "fd558d186df2c13a22455373858bae634a4795af",
              "versionType": "git"
            },
            {
              "lessThan": "a213a8950414c684999dcf03edeea6c46ede172e",
              "status": "affected",
              "version": "fd558d186df2c13a22455373858bae634a4795af",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/l2tp/l2tp_ppp.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.35"
            },
            {
              "lessThan": "2.6.35",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.94",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.36",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.13",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.94",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.36",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.13",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "2.6.35",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "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())."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerable path is reached through a local `ioctl()` on a connected PPPoL2TP `AF_PPPOX` socket. Remote L2TP packets do not invoke `pppol2tp_ioctl()`.\nAC:L - The attacker controls both sides of the race by blocking `copy_from_user()` in the ioctl thread and closing the same socket concurrently. No external victim state is required.\nPR:L - A local unprivileged user can reach the PPPoL2TP socket/ioctl path; L2TP management also uses user-namespace admin permissions rather than requiring real init-namespace root. This is not remotely reachable without local code execution.\nUI:N - No victim action is required after the attacker runs local code. The attacker creates/connects the socket, issues the ioctl, and closes the socket.\nS:U - The impact is within the kernel security authority on the same system. It is not a VM escape, IOMMU bypass, or cross-authority boundary violation.\nC:H - This is a kernel heap use-after-free of `struct l2tp_session`, and the resumed ioctl can read from reclaimed/faked session and tunnel data before copying results to userspace. Per conservative kernel UAF scoring, this supports high confidentiality impact.\nI:H - Kernel UAFs with attacker-controlled timing and heap reuse can be leveraged beyond a simple stale read, including corruption or control-flow primitives. When uncertain, the higher severity option is appropriate.\nA:H - At minimum, dereferencing the stale session or tunnel pointer can trigger a kernel oops or panic. The attacker can repeatedly trigger the race locally."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:34:40.148Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/78cdfdca88cbf731a92f3b9ee5427c633dd94e28"
        },
        {
          "url": "https://git.kernel.org/stable/c/e251d4cdfc725c9e7d686161e3b775a0e7d95053"
        },
        {
          "url": "https://git.kernel.org/stable/c/62f327e287cf7b595ae3f73ba72f5cd2a9e9f39f"
        },
        {
          "url": "https://git.kernel.org/stable/c/a213a8950414c684999dcf03edeea6c46ede172e"
        }
      ],
      "title": "l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-53262",
    "datePublished": "2026-06-25T08:39:50.550Z",
    "dateReserved": "2026-06-09T07:44:35.394Z",
    "dateUpdated": "2026-08-05T12:34:40.148Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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