CVE-2025-40271 (GCVE-0-2025-40271)

Vulnerability from cvelistv5 – Published: 2025-12-06 21:50 – Updated: 2026-08-05 12:09
VLAI
Title
fs/proc: fix uaf in proc_readdir_de()
Summary
In the Linux kernel, the following vulnerability has been resolved: fs/proc: fix uaf in proc_readdir_de() Pde is erased from subdir rbtree through rb_erase(), but not set the node to EMPTY, which may result in uaf access. We should use RB_CLEAR_NODE() set the erased node to EMPTY, then pde_subdir_next() will return NULL to avoid uaf access. We found an uaf issue while using stress-ng testing, need to run testcase getdent and tun in the same time. The steps of the issue is as follows: 1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current pde is tun3; 2) in the [time windows] unregister netdevice tun3 and tun2, and erase them from rbtree. erase tun3 first, and then erase tun2. the pde(tun2) will be released to slab; 3) continue to getdent process, then pde_subdir_next() will return pde(tun2) which is released, it will case uaf access. CPU 0 | CPU 1 ------------------------------------------------------------------------- traverse dir /proc/pid/net/dev_snmp6/ | unregister_netdevice(tun->dev) //tun3 tun2 sys_getdents64() | iterate_dir() | proc_readdir() | proc_readdir_de() | snmp6_unregister_dev() pde_get(de); | proc_remove() read_unlock(&proc_subdir_lock); | remove_proc_subtree() | write_lock(&proc_subdir_lock); [time window] | rb_erase(&root->subdir_node, &parent->subdir); | write_unlock(&proc_subdir_lock); read_lock(&proc_subdir_lock); | next = pde_subdir_next(de); | pde_put(de); | de = next; //UAF | rbtree of dev_snmp6 | pde(tun3) / \ NULL pde(tun2)
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-16 19:37 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7034 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 710585d4922fd315f2cada8fbe550ae8ed23e994 , < 1d1596d68a6f11d28f677eedf6cf5b17dbfeb491 (git)
Affected: 710585d4922fd315f2cada8fbe550ae8ed23e994 , < c81d0385500446efe48c305bbb83d47f2ae23a50 (git)
Affected: 710585d4922fd315f2cada8fbe550ae8ed23e994 , < 4cba73c4c89219beef7685a47374bf88b1022369 (git)
Affected: 710585d4922fd315f2cada8fbe550ae8ed23e994 , < 6f2482745e510ae1dacc9b090194b9c5f918d774 (git)
Affected: 710585d4922fd315f2cada8fbe550ae8ed23e994 , < 67272c11f379d9aa5e0f6b16286b9d89b3f76046 (git)
Affected: 710585d4922fd315f2cada8fbe550ae8ed23e994 , < 623bb26127fb581a741e880e1e1a47d79aecb6f8 (git)
Affected: 710585d4922fd315f2cada8fbe550ae8ed23e994 , < 03de7ff197a3d0e17d0d5c58fdac99a63cba8110 (git)
Affected: 710585d4922fd315f2cada8fbe550ae8ed23e994 , < 895b4c0c79b092d732544011c3cecaf7322c36a1 (git)
guessed Create a notification for this product.
Linux Linux Affected: 3.19
Unaffected: 0 , < 3.19 (semver)
Unaffected: 5.4.302 , ≤ 5.4.* (semver)
Unaffected: 5.10.247 , ≤ 5.10.* (semver)
Unaffected: 5.15.197 , ≤ 5.15.* (semver)
Unaffected: 6.1.159 , ≤ 6.1.* (semver)
Unaffected: 6.6.117 , ≤ 6.6.* (semver)
Unaffected: 6.12.59 , ≤ 6.12.* (semver)
Unaffected: 6.17.9 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Siemens RUGGEDCOM RST2428P Affected: 0 , < V4.0 (custom)
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\nfs/proc: fix uaf in proc_readdir_de()\n\nPde is erased from subdir rbtree through rb_erase(), but not set the node\nto EMPTY, which may result in uaf access.  We should use RB_CLEAR_NODE()\nset the erased node to EMPTY, then pde_subdir_next() will return NULL to\navoid uaf access.\n\nWe found an uaf issue while using stress-ng testing, need to run testcase\ngetdent and tun in the same time.  The steps of the issue is as follows:\n\n1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current\n   pde is tun3;\n\n2) in the [time windows] unregister netdevice tun3 and tun2, and erase\n   them from rbtree.  erase tun3 first, and then erase tun2.  the\n   pde(tun2) will be released to slab;\n\n3) continue to getdent process, then pde_subdir_next() will return\n   pde(tun2) which is released, it will case uaf access.\n\nCPU 0                                      |    CPU 1\n-------------------------------------------------------------------------\ntraverse dir /proc/pid/net/dev_snmp6/      |   unregister_netdevice(tun-\u003edev)   //tun3 tun2\nsys_getdents64()                           |\n  iterate_dir()                            |\n    proc_readdir()                         |\n      proc_readdir_de()                    |     snmp6_unregister_dev()\n        pde_get(de);                       |       proc_remove()\n        read_unlock(\u0026proc_subdir_lock);    |         remove_proc_subtree()\n                                           |           write_lock(\u0026proc_subdir_lock);\n        [time window]                      |           rb_erase(\u0026root-\u003esubdir_node, \u0026parent-\u003esubdir);\n                                           |           write_unlock(\u0026proc_subdir_lock);\n        read_lock(\u0026proc_subdir_lock);      |\n        next = pde_subdir_next(de);        |\n        pde_put(de);                       |\n        de = next;    //UAF                |\n\nrbtree of dev_snmp6\n                        |\n                    pde(tun3)\n                     /    \\\n                  NULL  pde(tun2)"
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad:\n\n\u0027\u0027\u0027\nfs/proc: fix uaf in proc_readdir_de()\n\u0027\u0027\u0027\n\nEl pde se elimina del subdir rbtree mediante rb_erase()**, pero no se establece el nodo a EMPTY, lo que puede resultar en acceso uaf. Deber\u00edamos usar RB_CLEAR_NODE()** para establecer el nodo eliminado a EMPTY, entonces pde_subdir_next()** devolver\u00e1 NULL para evitar acceso uaf.\n\nEncontramos un problema uaf mientras utiliz\u00e1bamos pruebas stress?ng, es necesario ejecutar el caso de prueba getdent y tun al mismo tiempo. Los pasos del problema son los siguientes:\n\n1) usar getdent para recorrer el directorio **/proc/pid/net/dev_snmp6/**, y el pde actual es tun3;  \n\n2) en la **[ventana de tiempo]** anular el registro del netdevice tun3 y tun2, y eliminarlos del rbtree. Eliminar tun3 primero, y luego eliminar tun2. El pde(tun2)** ser\u00e1 liberado al slab;  \n\n3) continuar el proceso getdent, entonces pde_subdir_next()** devolver\u00e1 pde(tun2)** que est\u00e1 liberado, lo que causar\u00e1 acceso uaf.\n\n\u0027\u0027\u0027\nCPU 0                                      |    CPU 1\n-------------------------------------------------------------------------\nrecorrer dir /proc/pid/net/dev_snmp6/      |   unregister_netdevice(tun -\u003e dev)   //tun3 tun2\nsys_getdents64()                           |\n  iterate_dir()                            |\n    proc_readdir()                         |\n      proc_readdir_de()                    |   snmp6_unregister_dev()\n        pde_get(de);                       |   proc_remove()\n        read_unlock(\u0026proc_subdir_lock);    |   remove_proc_subtree()\n                                           |   write_lock(\u0026proc_subdir_lock);\n        [ventana de tiempo]                |   rb_erase(\u0026root -\u003e subdir_node, \u0026parent -\u003e subdir);\n                                           |   write_unlock(\u0026proc_subdir_lock);\n        read_lock(\u0026proc_subdir_lock);      |\n        next = pde_subdir_next(de);        |\n        pde_put(de);                       |\n        de = next;    //UAF                |\n\u0027\u0027\u0027\n\nrbtree de dev_snmp6\n\u0027\u0027\u0027\n                        |\n                    pde(tun3)\n                     /    \\\n                  NULL  pde(tun2)\n\u0027\u0027\u0027"
          }
        ],
        "id": "CVE-2025-40271",
        "lastModified": "2026-10-15T19:10:00.173",
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              "cvssData": {
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                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
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      "current_release_date": "2026-07-30T08:37:53+00:00",
      "cve": "CVE-2025-40271",
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      "initial_release_date": "2025-12-06T00:00:00+00:00",
      "product_status:fixed": "2410",
      "product_status:known_affected": "22",
      "product_status:known_not_affected": "20",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: Linux kernel: Use-after-free in proc_readdir_de() can lead to privilege escalation or denial of service.",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40271.json",
      "version": "3"
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                    "versionType": "custom"
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              }
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            "providerMetadata": {
              "dateUpdated": "2026-06-02T13:00:17.378Z",
              "orgId": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
              "shortName": "siemens-SADP"
            },
            "references": [
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              }
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            "x_adpType": "supplier"
          },
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2025-40271",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
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                    "role": "CISA Coordinator",
                    "timestamp": "2026-06-16T19:37:49.226666Z",
                    "version": "2.0.3"
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              "dateUpdated": "2026-06-16T19:37:56.227Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
                "fs/proc/generic.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
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                  "version": "710585d4922fd315f2cada8fbe550ae8ed23e994",
                  "versionType": "git"
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                  "status": "affected",
                  "version": "710585d4922fd315f2cada8fbe550ae8ed23e994",
                  "versionType": "git"
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                {
                  "lessThan": "6f2482745e510ae1dacc9b090194b9c5f918d774",
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              "product": "Linux",
              "programFiles": [
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
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                  "version": "3.19"
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                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
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                  "status": "unaffected",
                  "version": "5.15.197",
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                  "lessThanOrEqual": "6.1.*",
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                  "status": "unaffected",
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                  "versionType": "original_commit_for_fix"
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                      "versionStartIncluding": "3.19",
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              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/proc: fix uaf in proc_readdir_de()\n\nPde is erased from subdir rbtree through rb_erase(), but not set the node\nto EMPTY, which may result in uaf access.  We should use RB_CLEAR_NODE()\nset the erased node to EMPTY, then pde_subdir_next() will return NULL to\navoid uaf access.\n\nWe found an uaf issue while using stress-ng testing, need to run testcase\ngetdent and tun in the same time.  The steps of the issue is as follows:\n\n1) use getdent to traverse dir /proc/pid/net/dev_snmp6/, and current\n   pde is tun3;\n\n2) in the [time windows] unregister netdevice tun3 and tun2, and erase\n   them from rbtree.  erase tun3 first, and then erase tun2.  the\n   pde(tun2) will be released to slab;\n\n3) continue to getdent process, then pde_subdir_next() will return\n   pde(tun2) which is released, it will case uaf access.\n\nCPU 0                                      |    CPU 1\n-------------------------------------------------------------------------\ntraverse dir /proc/pid/net/dev_snmp6/      |   unregister_netdevice(tun-\u003edev)   //tun3 tun2\nsys_getdents64()                           |\n  iterate_dir()                            |\n    proc_readdir()                         |\n      proc_readdir_de()                    |     snmp6_unregister_dev()\n        pde_get(de);                       |       proc_remove()\n        read_unlock(\u0026proc_subdir_lock);    |         remove_proc_subtree()\n                                           |           write_lock(\u0026proc_subdir_lock);\n        [time window]                      |           rb_erase(\u0026root-\u003esubdir_node, \u0026parent-\u003esubdir);\n                                           |           write_unlock(\u0026proc_subdir_lock);\n        read_lock(\u0026proc_subdir_lock);      |\n        next = pde_subdir_next(de);        |\n        pde_put(de);                       |\n        de = next;    //UAF                |\n\nrbtree of dev_snmp6\n                        |\n                    pde(tun3)\n                     /    \\\n                  NULL  pde(tun2)"
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  }
}



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