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eventpoll: fix ep_remove struct eventpoll / struct file UAF

Type: advisorySource: Official CVE List1 source record

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 i

Announced Source revision 1
Original source ↗

CVE-2026-46242

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-46242

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
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Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "f2451def095c1743adcfcb0cb5dadc86034e162a",
        "lessThan": "a10fbbe74e1c743beb1bb312109366667461df8a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "a1f93804449d13f97dabd4b996817de4bf1ed67a",
        "lessThan": "3e1144d2515d28e4312e663ea05eac203101491d",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "58c9b016e12855286370dfb704c08498edbc857a",
        "lessThan": "2de4db145b2992da496fea6c51f9839be678ae24",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "58c9b016e12855286370dfb704c08498edbc857a",
        "lessThan": "9324de74a3a59b9fde9b62ee45ebaa71458ba2e5",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "58c9b016e12855286370dfb704c08498edbc857a",
        "lessThan": "ef4ca02e95363e78977ca04340d44fe3b4b2b81f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "58c9b016e12855286370dfb704c08498edbc857a",
        "lessThan": "ced39b6a8062bac5c18a1c3df85634107eb8664a",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "58c9b016e12855286370dfb704c08498edbc857a",
        "lessThan": "a6dc643c69311677c574a0f17a3f4d66a5f3744b",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "5.15.209",
        "lessThan": "5.15.222",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "6.1.175",
        "lessThan": "6.1.178",
        "versionType": "semver"
      }
    ],
    "programFiles": [
      "fs/eventpoll.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "6.4"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "6.4",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.15.222",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.178",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.144",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.95",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.33",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.0.10",
        "versionType": "semver",
        "lessThanOrEqual": "7.0.*"
      },
      {
        "status": "unaffected",
        "version": "7.1",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "fs/eventpoll.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-46242

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#40161 · Revision 1
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