← Back to CVE Explorer

CVE-2025-39977

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: futex: Prevent use-after-free during requeue-PI syzbot managed to trigger the following race: T1 T2 futex_wait_requeue_pi() futex_do_wait() schedule() futex_requeue() futex_proxy_trylock_atomic() futex_requeue_pi_prepare() requeue_pi_wake_futex() futex_requeue_pi_complete() /* preempt */ * timeout/ signal wakes T1 * futex_requeue_pi_wakeup_sync() // Q_REQUEUE_PI_LOCKED futex_hash_put() // back to userland, on stack futex_q is garbage /* back */ wake_up_state(q->task, TASK_NORMAL); In this scenario futex_wait_requeue_pi() is able to leave without using futex_q::lock_ptr for synchronization. This can be prevented by reading futex_q::task before updating the futex_q::requeue_state. A reference on the task_struct is not needed because requeue_pi_wake_futex() is invoked with a spinlock_t held which implies a RCU read section. Even if T1 terminates immediately after, the task_struct will remain valid during T2's wake_up_state(). A READ_ONCE on futex_q::task before futex_requeue_pi_complete() is enough because it ensures that the variable is read before the state is updated. Read futex_q::task before updating the requeue state, use it for the following wakeup.

Severity
HIGH
CVSS score
7.8 (v3.1)
Vulnerability status
Deferred
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-10-15 08:15:35.517000
Last modified
2026-10-19 21:10:00.160000
View original CVE JSON 
{
  "id": "CVE-2025-39977",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2025-10-15T08:15:35.517",
  "lastModified": "2026-10-19T21:10:00.160",
  "vulnStatus": "Deferred",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Prevent use-after-free during requeue-PI\n\nsyzbot managed to trigger the following race:\n\n   T1                               T2\n\n futex_wait_requeue_pi()\n   futex_do_wait()\n     schedule()\n                               futex_requeue()\n                                 futex_proxy_trylock_atomic()\n                                   futex_requeue_pi_prepare()\n                                   requeue_pi_wake_futex()\n                                     futex_requeue_pi_complete()\n                                      /* preempt */\n\n         * timeout/ signal wakes T1 *\n\n   futex_requeue_pi_wakeup_sync() // Q_REQUEUE_PI_LOCKED\n   futex_hash_put()\n  // back to userland, on stack futex_q is garbage\n\n                                      /* back */\n                                     wake_up_state(q->task, TASK_NORMAL);\n\nIn this scenario futex_wait_requeue_pi() is able to leave without using\nfutex_q::lock_ptr for synchronization.\n\nThis can be prevented by reading futex_q::task before updating the\nfutex_q::requeue_state. A reference on the task_struct is not needed\nbecause requeue_pi_wake_futex() is invoked with a spinlock_t held which\nimplies a RCU read section.\n\nEven if T1 terminates immediately after, the task_struct will remain valid\nduring T2's wake_up_state().  A READ_ONCE on futex_q::task before\nfutex_requeue_pi_complete() is enough because it ensures that the variable\nis read before the state is updated.\n\nRead futex_q::task before updating the requeue state, use it for the\nfollowing wakeup."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nfutex: Prevenir uso después de liberación durante requeue-PI\n\nsyzbot logró activar la siguiente condición de carrera:\n\n   T1                               T2\n\n futex_wait_requeue_pi()\n   futex_do_wait()\n     schedule()\n                               futex_requeue()\n                                 futex_proxy_trylock_atomic()\n                                   futex_requeue_pi_prepare()\n                                   requeue_pi_wake_futex()\n                                     futex_requeue_pi_complete()\n                                      /* preempt */\n\n         * el tiempo de espera/la señal despierta a T1 *\n\n   futex_requeue_pi_wakeup_sync() // Q_REQUEUE_PI_LOCKED\n   futex_hash_put()\n  // de vuelta al espacio de usuario, en la pila futex_q es basura\n\n                                      /* de vuelta */\n                                     wake_up_state(q->task, TASK_NORMAL);\n\nEn este escenario, futex_wait_requeue_pi() puede salir sin usar futex_q::lock_ptr para la sincronización.\n\nEsto puede prevenirse leyendo futex_q::task antes de actualizar el futex_q::requeue_state. No se necesita una referencia en el task_struct porque se invoca a requeue_pi_wake_futex() con un spinlock_t mantenido, lo que implica una sección de lectura RCU.\n\nIncluso si T1 termina inmediatamente después, el task_struct permanecerá válido durante el wake_up_state() de T2. Un READ_ONCE en futex_q::task antes de futex_requeue_pi_complete() es suficiente porque asegura que la variable se lee antes de que se actualice el estado.\n\nLeer futex_q::task antes de actualizar el estado de requeue, usarlo para la siguiente activación."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "kernel/futex/requeue.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8",
              "lessThan": "cb5d19a61274b51b49601214a87af573b43d60fa",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8",
              "lessThan": "348736955ed6ca6e99ca24b93b1d3fbfe352c181",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8",
              "lessThan": "a170b9c0dde83312b8b58ccc91509c7c15711641",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8",
              "lessThan": "d824b2dbdcfe3c390278dd9652ea526168ef6850",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "07d91ef510fb16a2e0ca7453222105835b7ba3b8",
              "lessThan": "b549113738e8c751b613118032a724b772aa83f2",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "kernel/futex/requeue.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "5.15",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "5.15",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.155",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.109",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.50",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.16.10",
              "lessThanOrEqual": "6.16.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.17",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    },
    {
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
      "affectedData": [
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.5",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.6",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.7",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.5",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.6",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.7",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.5",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.6",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.7",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.5",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.6",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.7",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.5",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.6",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Siemens",
          "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP",
          "defaultStatus": "unknown",
          "versions": [
            {
              "version": "V3.1.7",
              "lessThan": "*",
              "versionType": "custom",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "attackVector": "LOCAL",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-10-15T21:55:38.918885Z",
          "id": "CVE-2025-39977",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/348736955ed6ca6e99ca24b93b1d3fbfe352c181",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/a170b9c0dde83312b8b58ccc91509c7c15711641",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/b549113738e8c751b613118032a724b772aa83f2",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/cb5d19a61274b51b49601214a87af573b43d60fa",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/d824b2dbdcfe3c390278dd9652ea526168ef6850",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html",
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
    },
    {
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html",
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
    },
    {
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-457936.html",
      "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
    }
  ]
}