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CVE-2026-46242 (GCVE-0-2026-46242)

Vulnerability from cvelistv5 – Published: 2026-05-30 12:13 – Updated: 2026-08-05 12:30
VLAI
Title
eventpoll: fix ep_remove struct eventpoll / struct file UAF
Summary
In the Linux kernel, the following vulnerability has been resolved: eventpoll: fix ep_remove struct eventpoll / struct file UAF ep_remove() (via ep_remove_file()) cleared file->f_ep under file->f_lock but then kept using @file inside the critical section (is_file_epoll(), hlist_del_rcu() through the head, spin_unlock). A concurrent __fput() taking the eventpoll_release() fastpath in that window observed the transient NULL, skipped eventpoll_release_file() and ran to f_op->release / file_free(). For the epoll-watches-epoll case, f_op->release is ep_eventpoll_release() -> ep_clear_and_put() -> ep_free(), which kfree()s the watched struct eventpoll. Its embedded ->refs hlist_head is exactly where epi->fllink.pprev points, so the subsequent hlist_del_rcu()'s "*pprev = next" scribbles into freed kmalloc-192 memory. In addition, struct file is SLAB_TYPESAFE_BY_RCU, so the slot backing @file could be recycled by alloc_empty_file() -- reinitializing f_lock and f_ep -- while ep_remove() is still nominally inside that lock. The upshot is an attacker-controllable kmem_cache_free() against the wrong slab cache. Pin @file via epi_fget() at the top of ep_remove() and gate the critical section on the pin succeeding. With the pin held @file cannot reach refcount zero, which holds __fput() off and transitively keeps the watched struct eventpoll alive across the hlist_del_rcu() and the f_lock use, closing both UAFs. If the pin fails @file has already reached refcount zero and its __fput() is in flight. Because we bailed before clearing f_ep, that path takes the eventpoll_release() slow path into eventpoll_release_file() and blocks on ep->mtx until the waiter side's ep_clear_and_put() drops it. The bailed epi's share of ep->refcount stays intact, so the trailing ep_refcount_dec_and_test() in ep_clear_and_put() cannot free the eventpoll out from under eventpoll_release_file(); the orphaned epi is then cleaned up there. A successful pin also proves we are not racing eventpoll_release_file() on this epi, so drop the now-redundant re-check of epi->dying under f_lock. The cheap lockless READ_ONCE(epi->dying) fast-path bailout stays.
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: a1f93804449d13f97dabd4b996817de4bf1ed67a , < 3e1144d2515d28e4312e663ea05eac203101491d (git)
Affected: 58c9b016e12855286370dfb704c08498edbc857a , < 2de4db145b2992da496fea6c51f9839be678ae24 (git)
Affected: 58c9b016e12855286370dfb704c08498edbc857a , < 9324de74a3a59b9fde9b62ee45ebaa71458ba2e5 (git)
Affected: 58c9b016e12855286370dfb704c08498edbc857a , < ef4ca02e95363e78977ca04340d44fe3b4b2b81f (git)
Affected: 58c9b016e12855286370dfb704c08498edbc857a , < ced39b6a8062bac5c18a1c3df85634107eb8664a (git)
Affected: 58c9b016e12855286370dfb704c08498edbc857a , < a6dc643c69311677c574a0f17a3f4d66a5f3744b (git)
Affected: f2451def095c1743adcfcb0cb5dadc86034e162a (git)
Affected: 6.1.175 , < 6.1.178 (semver)
Affected: 5.15.209 , < 5.16 (semver)
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Linux Linux Affected: 6.4
Unaffected: 0 , < 6.4 (semver)
Unaffected: 6.1.178 , ≤ 6.1.* (semver)
Unaffected: 6.6.144 , ≤ 6.6.* (semver)
Unaffected: 6.12.95 , ≤ 6.12.* (semver)
Unaffected: 6.18.33 , ≤ 6.18.* (semver)
Unaffected: 7.0.10 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\neventpoll: fix ep_remove struct eventpoll / struct file UAF\n\nep_remove() (via ep_remove_file()) cleared file-\u003ef_ep under\nfile-\u003ef_lock but then kept using @file inside the critical section\n(is_file_epoll(), hlist_del_rcu() through the head, spin_unlock).\nA concurrent __fput() taking the eventpoll_release() fastpath in\nthat window observed the transient NULL, skipped\neventpoll_release_file() and ran to f_op-\u003erelease / file_free().\n\nFor the epoll-watches-epoll case, f_op-\u003erelease is\nep_eventpoll_release() -\u003e ep_clear_and_put() -\u003e ep_free(), which\nkfree()s the watched struct eventpoll. Its embedded -\u003erefs\nhlist_head is exactly where epi-\u003efllink.pprev points, so the\nsubsequent hlist_del_rcu()\u0027s \"*pprev = next\" scribbles into freed\nkmalloc-192 memory.\n\nIn addition, struct file is SLAB_TYPESAFE_BY_RCU, so the slot\nbacking @file could be recycled by alloc_empty_file() --\nreinitializing f_lock and f_ep -- while ep_remove() is still\nnominally inside that lock. The upshot is an attacker-controllable\nkmem_cache_free() against the wrong slab cache.\n\nPin @file via epi_fget() at the top of ep_remove() and gate the\ncritical section on the pin succeeding. With the pin held @file\ncannot reach refcount zero, which holds __fput() off and\ntransitively keeps the watched struct eventpoll alive across the\nhlist_del_rcu() and the f_lock use, closing both UAFs.\n\nIf the pin fails @file has already reached refcount zero and its\n__fput() is in flight. Because we bailed before clearing f_ep,\nthat path takes the eventpoll_release() slow path into\neventpoll_release_file() and blocks on ep-\u003emtx until the waiter\nside\u0027s ep_clear_and_put() drops it. The bailed epi\u0027s share of\nep-\u003erefcount stays intact, so the trailing ep_refcount_dec_and_test()\nin ep_clear_and_put() cannot free the eventpoll out from under\neventpoll_release_file(); the orphaned epi is then cleaned up\nthere.\n\nA successful pin also proves we are not racing\neventpoll_release_file() on this epi, so drop the now-redundant\nre-check of epi-\u003edying under f_lock. The cheap lockless\nREAD_ONCE(epi-\u003edying) fast-path bailout stays."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\neventpoll: correcci\u00f3n de UAF de struct eventpoll / struct file en ep_remove\n\nep_remove() (a trav\u00e9s de ep_remove_file()) limpi\u00f3 file-\u003ef_ep bajo file-\u003ef_lock pero luego sigui\u00f3 usando @file dentro de la secci\u00f3n cr\u00edtica (is_file_epoll(), hlist_del_rcu() a trav\u00e9s del encabezado, spin_unlock). Un __fput() concurrente que tomaba la ruta r\u00e1pida de eventpoll_release() en esa ventana observ\u00f3 el NULL transitorio, omiti\u00f3 eventpoll_release_file() y se ejecut\u00f3 a f_op-\u003erelease / file_free().\n\nPara el caso de epoll-observa-epoll, f_op-\u003erelease es ep_eventpoll_release() -\u003e ep_clear_and_put() -\u003e ep_free(), que libera con kfree() la struct eventpoll observada. Su hlist_head -\u003erefs incrustada es exactamente donde apunta epi-\u003efllink.pprev, por lo que el \"*pprev = next\" del hlist_del_rcu() subsiguiente escribe en memoria kmalloc-192 liberada.\n\nAdem\u00e1s, struct file es SLAB_TYPESAFE_BY_RCU, por lo que el slot que respalda a @file podr\u00eda ser reciclado por alloc_empty_file() -- reinicializando f_lock y f_ep -- mientras ep_remove() todav\u00eda est\u00e1 nominalmente dentro de ese bloqueo. El resultado es un kmem_cache_free() controlable por un atacante contra la cach\u00e9 de slab incorrecta.\n\nFija @file a trav\u00e9s de epi_fget() al inicio de ep_remove() y condiciona la secci\u00f3n cr\u00edtica al \u00e9xito de la fijaci\u00f3n. Con la fijaci\u00f3n mantenida, @file no puede alcanzar un recuento de referencias de cero, lo que evita que __fput() se ejecute y mantiene transitivamente viva la struct eventpoll observada a trav\u00e9s del hlist_del_rcu() y el uso de f_lock, cerrando ambas UAFs.\n\nSi la fijaci\u00f3n falla, @file ya ha alcanzado un recuento de referencias de cero y su __fput() est\u00e1 en curso. Debido a que abortamos antes de limpiar f_ep, esa ruta toma la ruta lenta de eventpoll_release() hacia eventpoll_release_file() y se bloquea en ep-\u003emtx hasta que el ep_clear_and_put() del lado del esperador lo suelta. La parte de ep-\u003erefcount del epi abortado permanece intacta, por lo que el ep_refcount_dec_and_test() final en ep_clear_and_put() no puede liberar el eventpoll por debajo de eventpoll_release_file(); el epi hu\u00e9rfano es entonces limpiado all\u00ed.\n\nUna fijaci\u00f3n exitosa tambi\u00e9n prueba que no estamos compitiendo con eventpoll_release_file() en este epi, por lo que se elimina la ahora redundante nueva verificaci\u00f3n de epi-\u003edying bajo f_lock. La salida r\u00e1pida barata sin bloqueo de READ_ONCE(epi-\u003edying) permanece."
          }
        ],
        "id": "CVE-2026-46242",
        "lastModified": "2026-07-24T15:17:22.733",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-05-30T13:16:21.980",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/2de4db145b2992da496fea6c51f9839be678ae24"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/3e1144d2515d28e4312e663ea05eac203101491d"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/9324de74a3a59b9fde9b62ee45ebaa71458ba2e5"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/a6dc643c69311677c574a0f17a3f4d66a5f3744b"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/ced39b6a8062bac5c18a1c3df85634107eb8664a"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/ef4ca02e95363e78977ca04340d44fe3b4b2b81f"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "url": "http://www.openwall.com/lists/oss-security/2026/07/08/14"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-416"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-08-31T14:49:25+00:00",
      "cve": "CVE-2026-46242",
      "id": "CVE-2026-46242",
      "initial_release_date": "2026-05-30T00:00:00+00:00",
      "product_status:fixed": "1603",
      "product_status:known_affected": "1",
      "product_status:known_not_affected": "112",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: eventpoll: fix ep_remove struct eventpoll / struct file UAF",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46242.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-20T00:02:20Z",
      "cve": "CVE-2026-46242",
      "id": "CVE-2026-46242",
      "initial_release_date": "2026-05-31T01:32:25Z",
      "product_status:first_fixed": "2",
      "product_status:known_affected": "394",
      "product_status:known_not_affected": "279",
      "product_status:recommended": "537",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-46242",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-46242.json",
      "version": "25"
    }
  }
}



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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.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.