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CVE-2025-39840

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: audit: fix out-of-bounds read in audit_compare_dname_path() When a watch on dir=/ is combined with an fsnotify event for a single-character name directly under / (e.g., creating /a), an out-of-bounds read can occur in audit_compare_dname_path(). The helper parent_len() returns 1 for "/". In audit_compare_dname_path(), when parentlen equals the full path length (1), the code sets p = path + 1 and pathlen = 1 - 1 = 0. The subsequent loop then dereferences p[pathlen - 1] (i.e., p[-1]), causing an out-of-bounds read. Fix this by adding a pathlen > 0 check to the while loop condition to prevent the out-of-bounds access. [PM: subject tweak, sign-off email fixes]

Severity
HIGH
CVSS score
7.1 (v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-09-19 16:15:42.703000
Last modified
2026-10-19 21:10:00.160000
View original CVE JSON 
{
  "id": "CVE-2025-39840",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2025-09-19T16:15:42.703",
  "lastModified": "2026-10-19T21:10:00.160",
  "vulnStatus": "Modified",
  "cveTags": [],
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    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\naudit: fix out-of-bounds read in audit_compare_dname_path()\n\nWhen a watch on dir=/ is combined with an fsnotify event for a\nsingle-character name directly under / (e.g., creating /a), an\nout-of-bounds read can occur in audit_compare_dname_path().\n\nThe helper parent_len() returns 1 for \"/\". In audit_compare_dname_path(),\nwhen parentlen equals the full path length (1), the code sets p = path + 1\nand pathlen = 1 - 1 = 0. The subsequent loop then dereferences\np[pathlen - 1] (i.e., p[-1]), causing an out-of-bounds read.\n\nFix this by adding a pathlen > 0 check to the while loop condition\nto prevent the out-of-bounds access.\n\n[PM: subject tweak, sign-off email fixes]"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\naudit: corregir lectura fuera de límites en audit_compare_dname_path()\n\nCuando una vigilancia en dir=/ se combina con un evento fsnotify para un nombre de un solo carácter directamente bajo / (p. ej., al crear /a), puede ocurrir una lectura fuera de límites en audit_compare_dname_path().\n\nLa función auxiliar parent_len() devuelve 1 para '/'. En audit_compare_dname_path(), cuando parentlen es igual a la longitud completa de la ruta (1), el código establece p = path + 1 y pathlen = 1 - 1 = 0. El bucle subsiguiente entonces desreferencia p[pathlen - 1] (es decir, p[-1]), causando una lectura fuera de límites.\n\nCorregir esto añadiendo una comprobación pathlen > 0 a la condición del bucle while para prevenir el acceso fuera de límites.\n\n[PM: ajuste del asunto, correcciones de correo electrónico de aprobación]"
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