{
  "schemaVersion": 1,
  "attribution": [
    {
      "source": "CISA Known Exploited Vulnerabilities",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "licence": "US government work"
    },
    {
      "source": "GitHub Advisory Database",
      "url": "https://github.com/advisories",
      "licence": "CC BY 4.0"
    },
    {
      "source": "Have I Been Pwned",
      "url": "https://haveibeenpwned.com/",
      "licence": "CC BY 4.0"
    },
    {
      "source": "CVE Program (CVE records)",
      "url": "https://www.cve.org/Legal/TermsOfUse",
      "licence": "CVE Terms of Use",
      "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.",
      "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss/",
      "licence": "free to use; FIRST requests attribution"
    }
  ],
  "record": {
    "id": "CVE-2026-63918",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-63918",
    "idYear": 2026,
    "status": "PUBLISHED",
    "publishedAt": "2026-07-19T14:55:21.414Z",
    "updatedAt": "2026-08-05T12:37:12.656Z",
    "importedAt": "2026-10-24T01:58:25.636Z",
    "snapshot": {
      "id": "cve_2026-10-24_midnight_baseline",
      "at": "2026-10-24T00:00:00.000Z",
      "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"
    },
    "facts": {
      "title": "l2tp: use refcount_inc_not_zero in l2tp_session_get_by_ifname",
      "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nl2tp: use refcount_inc_not_zero in l2tp_session_get_by_ifname\n\nA reader in l2tp_session_get_by_ifname() can return a pointer to a\nsession whose refcount has reached zero. The getter takes its\nreference with plain refcount_inc(), but every other session getter\nin the same file (l2tp_v2_session_get, l2tp_v3_session_get, and the\ncorresponding _get_next variants) uses refcount_inc_not_zero()\nbecause the IDR/RCU lookup can race with refcount_dec_and_test() ->\nl2tp_session_free() -> kfree_rcu(). The ifname getter is the only\noutlier; the inconsistency was raised on-list after 979c017803c4\n(\"l2tp: use list_del_rcu in l2tp_session_unhash\").\n\nA reader inside rcu_read_lock_bh() that matches session->ifname can\nbe preempted between the strcmp() and the refcount_inc(). If the\nlast reference drops on another CPU in that window, the reader's\nrefcount_inc() runs on a counter that has reached zero. refcount_t\ncatches the addition-on-zero, prints \"refcount_t: addition on 0;\nuse-after-free\", saturates the counter, and returns the saturated\npointer to the caller. Session memory is held live by the in-flight\nRCU read section, but the kfree_rcu() callback queued from\nl2tp_session_free() will free it once the grace period closes; a\ncaller that dereferences the returned session past that point hits\na slab-use-after-free. On PREEMPT_RT local_bh_disable() is a per-CPU\nsleeping lock and the preemption window is real; on stock PREEMPT\nkernels local_bh_disable() is a preempt_count increment that closes\nthe cross-CPU race in practice (see below).\n\nUse refcount_inc_not_zero() and continue the list walk on failure,\nmatching the other session getters in the file. The ifname getter\nis the only session getter in net/l2tp/ that still uses the bare\nrefcount_inc() pattern; this change restores file-internal\nconsistency. The success path is unchanged.",
      "affected": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "abe7a1a7d0b69e63b1bca5f9531023a52336784f",
              "status": "affected",
              "versionType": "git",
              "lessThan": "ee80455feffb9cb62b5b58715cabeff495e666b2"
            },
            {
              "version": "abe7a1a7d0b69e63b1bca5f9531023a52336784f",
              "status": "affected",
              "versionType": "git",
              "lessThan": "947013fd7c8c35dd5856557b215840098a3f67f8"
            },
            {
              "version": "abe7a1a7d0b69e63b1bca5f9531023a52336784f",
              "status": "affected",
              "versionType": "git",
              "lessThan": "782d60a6596aee9b29c2eecfa70033899278bf65"
            },
            {
              "version": "abe7a1a7d0b69e63b1bca5f9531023a52336784f",
              "status": "affected",
              "versionType": "git",
              "lessThan": "05f95729ca844704d15e49ce14868af4b403b32b"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "versions": [
            {
              "version": "6.12",
              "status": "affected"
            },
            {
              "version": "0",
              "status": "unaffected",
              "versionType": "semver",
              "lessThan": "6.12"
            },
            {
              "version": "6.12.93",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "version": "6.18.35",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "version": "7.0.12",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "7.0.*"
            },
            {
              "version": "7.1",
              "status": "unaffected",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ]
        }
      ]
    }
  }
}