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 7033 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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      "product_status:known_not_affected": "99",
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      "source": "SUSE CSAF VEX",
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      "title": "SUSE CVE CVE-2025-40271",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2025/cve-2025-40271.json",
      "version": "54"
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                    "status": "affected",
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                    "versionType": "custom"
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            "providerMetadata": {
              "dateUpdated": "2026-06-02T13:00:17.378Z",
              "orgId": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
              "shortName": "siemens-SADP"
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            "references": [
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            "x_adpType": "supplier"
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          {
            "metrics": [
              {
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                  "content": {
                    "id": "CVE-2025-40271",
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                      {
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              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
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            "title": "CISA ADP Vulnrichment"
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        ],
        "cna": {
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              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
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              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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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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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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

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