FKIE_CVE-2026-74637

Vulnerability from fkie_nvd - Published: 2026-08-22 16:16 - Updated: 2026-10-14 13:10
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: perf/core: Fix group leader use-after-free after sibling detach perf_group_detach() handles leader and sibling detach differently. When the group leader is detached, all siblings are promoted to singleton events and their group_leader pointer is reset to themselves. When a sibling is detached, it is removed from the leader's sibling_list, but its group_leader pointer is left pointing at the old leader. That is harmless when the sibling is being closed and freed immediately, as in the DETACH_DEAD path. It is not safe when the sibling is detached but kept alive, such as during CPU hotplug with DETACH_GROUP. In that case the sibling is removed from the context, while its file descriptor can still keep it alive. A typical failing sequence is: - A group contains leader L and sibling S. - CPU hot-unplug detaches S with DETACH_GROUP, removing it from L->sibling_list but leaving S->group_leader == L. - L is later closed and freed. - A PERF_IOC_FLAG_GROUP ioctl on S follows S->group_leader and dereferences the freed leader. This was reproduced by running the perf event fuzzer, CPU hotplug, and a stress workload concurrently: Unable to handle kernel paging request at virtual address 006b6b6b6b6b6cdb CPU: 2 PID: 12489 Comm: perf_fuzzer 6.18.7 PREEMPT pc : perf_ioctl+0x34c/0xc68 x20: ffffff89a3fa2c70 x8 : 6b6b6b6b6b6b6b6b Code: 943c4a0e 340047a0 f9404a94 f9411e88 (f940b908) Call trace: perf_ioctl+0x34c/0xc68 (P) __arm64_sys_ioctl+0xa0/0xf4 invoke_syscall+0x58/0xe4 el0_svc_common+0xa8/0xdc do_el0_svc+0x1c/0x28 el0_svc+0x40/0xc0 el0t_64_sync_handler+0x68/0xdc el0t_64_sync+0x1c4/0x1c8 The fault happened in perf_ioctl(), where perf_event_for_each() follows the stale group_leader pointer and perf_event_for_each_child() then dereferences the freed leader's context. Fix the use-after-free by promoting the detached sibling to a singleton. Also fix __event_disable() cgroup accounting and event state change.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1e7abfeb23c12bf46f6457e4a3e1a1a300d50619
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/42c5ca1f0a288a52878bd72a5595b08261057438
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/80c6054a4c40a0ffad82acef9f9a0dee108d152a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8e92e03984364d93e0d5b0acd81c95eca773f034
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8f867c0e8da4c2303d91adf45acb6b1820966c27
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a979a642402d0b1f856c7a729b4cb2d92de4cf2f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b42948f9e0d1ea4dbd5742ce1dfc7688de5d4a35
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f8a07021679aadfb6d63b209207ccc41f26982d1
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/events/core.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "8f867c0e8da4c2303d91adf45acb6b1820966c27",
              "status": "affected",
              "version": "8a49542c0554af7d0073aac0ee73ee65b807ef34",
              "versionType": "git"
            },
            {
              "lessThan": "8e92e03984364d93e0d5b0acd81c95eca773f034",
              "status": "affected",
              "version": "8a49542c0554af7d0073aac0ee73ee65b807ef34",
              "versionType": "git"
            },
            {
              "lessThan": "f8a07021679aadfb6d63b209207ccc41f26982d1",
              "status": "affected",
              "version": "8a49542c0554af7d0073aac0ee73ee65b807ef34",
              "versionType": "git"
            },
            {
              "lessThan": "80c6054a4c40a0ffad82acef9f9a0dee108d152a",
              "status": "affected",
              "version": "8a49542c0554af7d0073aac0ee73ee65b807ef34",
              "versionType": "git"
            },
            {
              "lessThan": "b42948f9e0d1ea4dbd5742ce1dfc7688de5d4a35",
              "status": "affected",
              "version": "8a49542c0554af7d0073aac0ee73ee65b807ef34",
              "versionType": "git"
            },
            {
              "lessThan": "a979a642402d0b1f856c7a729b4cb2d92de4cf2f",
              "status": "affected",
              "version": "8a49542c0554af7d0073aac0ee73ee65b807ef34",
              "versionType": "git"
            },
            {
              "lessThan": "1e7abfeb23c12bf46f6457e4a3e1a1a300d50619",
              "status": "affected",
              "version": "8a49542c0554af7d0073aac0ee73ee65b807ef34",
              "versionType": "git"
            },
            {
              "lessThan": "42c5ca1f0a288a52878bd72a5595b08261057438",
              "status": "affected",
              "version": "8a49542c0554af7d0073aac0ee73ee65b807ef34",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "e732ebc42aea321ee84514330eb3a675307fcc83",
              "versionType": "git"
            },
            {
              "lessThan": "2.6.35",
              "status": "affected",
              "version": "2.6.34.14",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/events/core.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": "5.10.*",
              "status": "unaffected",
              "version": "5.10.267",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.218",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.185",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.154",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.105",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.45",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf/core: Fix group leader use-after-free after sibling detach\n\nperf_group_detach() handles leader and sibling detach differently. When the\ngroup leader is detached, all siblings are promoted to singleton events and\ntheir group_leader pointer is reset to themselves. When a sibling is\ndetached, it is removed from the leader\u0027s sibling_list, but its\ngroup_leader pointer is left pointing at the old leader.\n\nThat is harmless when the sibling is being closed and freed immediately, as\nin the DETACH_DEAD path. It is not safe when the sibling is detached but\nkept alive, such as during CPU hotplug with DETACH_GROUP. In that case the\nsibling is removed from the context, while its file descriptor can still\nkeep it alive.\n\nA typical failing sequence is:\n\n  - A group contains leader L and sibling S.\n  - CPU hot-unplug detaches S with DETACH_GROUP, removing it from\n    L-\u003esibling_list but leaving S-\u003egroup_leader == L.\n  - L is later closed and freed.\n  - A PERF_IOC_FLAG_GROUP ioctl on S follows S-\u003egroup_leader and\n    dereferences the freed leader.\n\nThis was reproduced by running the perf event fuzzer, CPU hotplug, and a\nstress workload concurrently:\n\n  Unable to handle kernel paging request at virtual address 006b6b6b6b6b6cdb\n  CPU: 2 PID: 12489 Comm: perf_fuzzer 6.18.7 PREEMPT\n  pc : perf_ioctl+0x34c/0xc68\n  x20: ffffff89a3fa2c70 x8 : 6b6b6b6b6b6b6b6b\n  Code: 943c4a0e 340047a0 f9404a94 f9411e88 (f940b908)\n  Call trace:\n  perf_ioctl+0x34c/0xc68 (P)\n  __arm64_sys_ioctl+0xa0/0xf4\n  invoke_syscall+0x58/0xe4\n  el0_svc_common+0xa8/0xdc\n  do_el0_svc+0x1c/0x28\n  el0_svc+0x40/0xc0\n  el0t_64_sync_handler+0x68/0xdc\n  el0t_64_sync+0x1c4/0x1c8\n\nThe fault happened in perf_ioctl(), where perf_event_for_each() follows\nthe stale group_leader pointer and perf_event_for_each_child() then\ndereferences the freed leader\u0027s context.\n\nFix the use-after-free by promoting the detached sibling to a singleton.\nAlso fix __event_disable() cgroup accounting and event state change."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nperf/core: Soluci\u00f3n para el uso despu\u00e9s de liberaci\u00f3n del l\u00edder de grupo tras la desvinculaci\u00f3n del hermano\n\nperf_group_detach() maneja la desvinculaci\u00f3n del l\u00edder y del hermano de manera diferente. Cuando el l\u00edder de grupo se desvincula, todos los hermanos son promovidos a eventos singleton y su puntero group_leader se restablece a s\u00ed mismos. Cuando un hermano se desvincula, se elimina de la sibling_list del l\u00edder, pero su puntero group_leader se deja apuntando al antiguo l\u00edder.\n\nEsto es inofensivo cuando el hermano se est\u00e1 cerrando y liberando inmediatamente, como en la ruta DETACH_DEAD. No es seguro cuando el hermano se desvincula pero se mantiene vivo, como durante el hotplug de CPU con DETACH_GROUP. En ese caso, el hermano se elimina del contexto, mientras que su descriptor de archivo a\u00fan puede mantenerlo vivo.\n\nUna secuencia de fallo t\u00edpica es:\n\n  - Un grupo contiene el l\u00edder L y el hermano S.\n  - El hot-unplug de CPU desvincula S con DETACH_GROUP, elimin\u00e1ndolo de L -\u003e sibling_list pero dejando S -\u003e group_leader == L.\n  - L se cierra y libera m\u00e1s tarde.\n  - Un ioctl PERF_IOC_FLAG_GROUP en S sigue a S -\u003e group_leader y desreferencia al l\u00edder liberado.\n\nEsto se reprodujo ejecutando el fuzzer de eventos perf, el hotplug de CPU y una carga de trabajo de estr\u00e9s concurrentemente:\n\n  Unable to handle kernel paging request at virtual address 006b6b6b6b6b6cdb\n  CPU: 2 PID: 12489 Comm: perf_fuzzer 6.18.7 PREEMPT\n  pc : perf_ioctl+0x34c/0xc68\n  x20: ffffff89a3fa2c70 x8 : 6b6b6b6b6b6b6b6b\n  Code: 943c4a0e 340047a0 f9404a94 f9411e88 (f940b908)\n  Call trace:\n  perf_ioctl+0x34c/0xc68 (P)\n  __arm64_sys_ioctl+0xa0/0xf4\n  invoke_syscall+0x58/0xe4\n  el0_svc_common+0xa8/0xdc\n  do_el0_svc+0x1c/0x28\n  el0_svc+0x40/0xc0\n  el0t_64_sync_handler+0x68/0xdc\n  el0t_64_sync+0x1c4/0x1c8\n\nEl fallo ocurri\u00f3 en perf_ioctl(), donde perf_event_for_each() sigue el puntero group_leader obsoleto y perf_event_for_each_child() luego desreferencia el contexto del l\u00edder liberado.\n\nSoluciona el uso despu\u00e9s de liberaci\u00f3n promoviendo al hermano desvinculado a un singleton. Tambi\u00e9n corrige la contabilidad de cgroup de __event_disable() y el cambio de estado del evento."
    }
  ],
  "id": "CVE-2026-74637",
  "lastModified": "2026-10-14T13:10:00.187",
  "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": "2026-08-22T16:16:36.890",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/1e7abfeb23c12bf46f6457e4a3e1a1a300d50619"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/42c5ca1f0a288a52878bd72a5595b08261057438"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/80c6054a4c40a0ffad82acef9f9a0dee108d152a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8e92e03984364d93e0d5b0acd81c95eca773f034"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8f867c0e8da4c2303d91adf45acb6b1820966c27"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a979a642402d0b1f856c7a729b4cb2d92de4cf2f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b42948f9e0d1ea4dbd5742ce1dfc7688de5d4a35"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f8a07021679aadfb6d63b209207ccc41f26982d1"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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