CVE-2025-40214

Estado: AplazadaAlta (7.8)—

In the Linux kernel, the following vulnerability has been resolved:

af_unix: Initialise scc_index in unix_add_edge().

Quang Le reported that the AF_UNIX GC could garbage-collect a receive queue of an alive in-flight socket, with a nice repro.

The repro consists of three stages.

As of 2-c, sk-A and sk-X are linked to unix_unvisited_vertices, and unix_walk_scc() groups them into two different SCCs:

Once GC completes, unix_graph_grouped is set to true. Also, unix_graph_maybe_cyclic is set to true due to sk-X's cyclic self-reference, which makes close() trigger GC.

At 3-b, unix_add_edge() allocates unix_sk(sk-B)->vertex and links it to unix_unvisited_vertices.

Leer descripción completaMostrar menos

unix_update_graph() is called at 3-a. and 3-b., but neither unix_graph_grouped nor unix_graph_maybe_cyclic is changed because both sk-B's listener and sk-C are not in-flight.

3-c decrements sk-A's file refcnt to 1.

Since unix_graph_grouped is true at 3-d, unix_walk_scc_fast() is finally called and iterates 3 sockets sk-A, sk-B, and sk-X:

This is totally fine. All of them are not yet close()d and should be grouped into different SCCs.

However, unix_vertex_dead() misjudges that sk-A and sk-B are in the same SCC and sk-A is dead.

The problem is that unix_add_edge() does not initialise scc_index.

Stage 1) is used for heap spraying, making a newly allocated vertex have vertex->scc_index == 2 (UNIX_VERTEX_INDEX_START) set by unix_walk_scc() at 1-c.

Let's track the max SCC index from the previous unix_walk_scc() call and assign the max + 1 to a new vertex's scc_index.

This way, we can continue to avoid Tarjan's algorithm while preventing misjudgments.

Detalles técnicos trazas, registros y código del informe original

  1)
    1-a. Create a single cyclic reference with many sockets
    1-b. close() all sockets
    1-c. Trigger GC

  2)
    2-a. Pass sk-A to an embryo sk-B
    2-b. Pass sk-X to sk-X
    2-c. Trigger GC

  3)
    3-a. accept() the embryo sk-B
    3-b. Pass sk-B to sk-C
    3-c. close() the in-flight sk-A
    3-d. Trigger GC

  unix_sk(sk-A)->vertex->scc_index = 2 (UNIX_VERTEX_INDEX_START)
  unix_sk(sk-X)->vertex->scc_index = 3

  sk-A -> sk-B (-> sk-C)
  sk-X -> sk-X

  unix_sk(sk-A)->scc_index == unix_sk(sk-B)->scc_index <-- Wrong!
  &&
  sk-A's file refcnt == unix_sk(sk-A)->vertex->out_degree
                                       ^-- 1 in-flight count for sk-B
  -> sk-A is dead !?

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 7.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.15%
Percentil entre todas las CVEs puntuadas: 3
Fecha de la puntuación: 6/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1068 Exploitation for Privilege Escalationprivilege escalation85 %
Impacto principalT1499.004 Application or System Exploitationimpact75 %
Impacto secundarioT1565.001 Stored Data Manipulationimpact60 %

Vulnerabilidad local (AV:L/PR:L) en garbage collector del kernel que permite a un atacante con privilegios locales causar DoS por corrupción de memoria de sockets en vuelo, o potencialmente manipular datos en cola de recepción.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Threat Intelligence Program Restrict File and Directory Permissions Remote Data Storage Filter Network Traffic Execution Prevention Encrypt Sensitive Information

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Linux — Linux Kernel^AI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2025-40214",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
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        "impactScore": 5.9,
        "exploitabilityScore": 1.8
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          "product": "RUGGEDCOM RST2428P",
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  "published": "2025-12-04T13:15:48.157",
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      "url": "https://git.kernel.org/stable/c/1aa7e40ee850c9053e769957ce6541173891204d",
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    {
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  ],
  "vulnStatus": "Deferred",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\naf_unix: Initialise scc_index in unix_add_edge().\n\nQuang Le reported that the AF_UNIX GC could garbage-collect a\nreceive queue of an alive in-flight socket, with a nice repro.\n\nThe repro consists of three stages.\n\n  1)\n    1-a. Create a single cyclic reference with many sockets\n    1-b. close() all sockets\n    1-c. Trigger GC\n\n  2)\n    2-a. Pass sk-A to an embryo sk-B\n    2-b. Pass sk-X to sk-X\n    2-c. Trigger GC\n\n  3)\n    3-a. accept() the embryo sk-B\n    3-b. Pass sk-B to sk-C\n    3-c. close() the in-flight sk-A\n    3-d. Trigger GC\n\nAs of 2-c, sk-A and sk-X are linked to unix_unvisited_vertices,\nand unix_walk_scc() groups them into two different SCCs:\n\n  unix_sk(sk-A)->vertex->scc_index = 2 (UNIX_VERTEX_INDEX_START)\n  unix_sk(sk-X)->vertex->scc_index = 3\n\nOnce GC completes, unix_graph_grouped is set to true.\nAlso, unix_graph_maybe_cyclic is set to true due to sk-X's\ncyclic self-reference, which makes close() trigger GC.\n\nAt 3-b, unix_add_edge() allocates unix_sk(sk-B)->vertex and\nlinks it to unix_unvisited_vertices.\n\nunix_update_graph() is called at 3-a. and 3-b., but neither\nunix_graph_grouped nor unix_graph_maybe_cyclic is changed\nbecause both sk-B's listener and sk-C are not in-flight.\n\n3-c decrements sk-A's file refcnt to 1.\n\nSince unix_graph_grouped is true at 3-d, unix_walk_scc_fast()\nis finally called and iterates 3 sockets sk-A, sk-B, and sk-X:\n\n  sk-A -> sk-B (-> sk-C)\n  sk-X -> sk-X\n\nThis is totally fine.  All of them are not yet close()d and\nshould be grouped into different SCCs.\n\nHowever, unix_vertex_dead() misjudges that sk-A and sk-B are\nin the same SCC and sk-A is dead.\n\n  unix_sk(sk-A)->scc_index == unix_sk(sk-B)->scc_index <-- Wrong!\n  &&\n  sk-A's file refcnt == unix_sk(sk-A)->vertex->out_degree\n                                       ^-- 1 in-flight count for sk-B\n  -> sk-A is dead !?\n\nThe problem is that unix_add_edge() does not initialise scc_index.\n\nStage 1) is used for heap spraying, making a newly allocated\nvertex have vertex->scc_index == 2 (UNIX_VERTEX_INDEX_START)\nset by unix_walk_scc() at 1-c.\n\nLet's track the max SCC index from the previous unix_walk_scc()\ncall and assign the max + 1 to a new vertex's scc_index.\n\nThis way, we can continue to avoid Tarjan's algorithm while\npreventing misjudgments."
    }
  ],
  "lastModified": "2026-07-30T06:24:18.343",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}