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CVE-2025-39735

Estado: ModificadaAlta (7.1)—

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

jfs: fix slab-out-of-bounds read in ea_get()

During the "size_check" label in ea_get(), the code checks if the extended attribute list (xattr) size matches ea_size. If not, it logs "ea_get: invalid extended attribute" and calls print_hex_dump().

Here, EALIST_SIZE(ea_buf->xattr) returns 4110417968, which exceeds INT_MAX (2,147,483,647). Then ea_size is clamped:

Although clamp_t aims to bound ea_size between 0 and 4110417968, the upper limit is treated as an int, causing an overflow above 2^31 - 1. This leads "size" to wrap around and become negative (-184549328).

Leer descripción completaMostrar menos

The "size" is then passed to print_hex_dump() (called "len" in print_hex_dump()), it is passed as type size_t (an unsigned type), this is then stored inside a variable called "int remaining", which is then assigned to "int linelen" which is then passed to hex_dump_to_buffer(). In print_hex_dump() the for loop, iterates through 0 to len-1, where len is 18446744073525002176, calling hex_dump_to_buffer() on each iteration:

The expected stopping condition (i < len) is effectively broken since len is corrupted and very large. This eventually leads to the "ptr+i" being passed to hex_dump_to_buffer() to get closer to the end of the actual bounds of "ptr", eventually an out of bounds access is done in hex_dump_to_buffer() in the following for loop:

To fix this we should validate "EALIST_SIZE(ea_buf->xattr)" before it is utilised.

Detalles técnicos trazas, registros y código del informe original
	int size = clamp_t(int, ea_size, 0, EALIST_SIZE(ea_buf->xattr));

	for (i = 0; i < len; i += rowsize) {
		linelen = min(remaining, rowsize);
		remaining -= rowsize;

		hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
				   linebuf, sizeof(linebuf), ascii);

		...
	}

	for (j = 0; j < len; j++) {
			if (linebuflen < lx + 2)
				goto overflow2;
			ch = ptr[j];
		...
	}

CVSS

Probabilidad de explotación (EPSS)

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.

Vulnerabilidad local (AV:L/PR:L) que causa lectura fuera de límites (slab-out-of-bounds) en el kernel Linux. Acceso local con privilegios usuario permite escalada mediante corrupción de memoria.

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 ProgramExecution PreventionApplication Isolation and SandboxingExploit ProtectionUpdate SoftwareData Loss Prevention

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\njfs: fix slab-out-of-bounds read in ea_get()\n\nDuring the \"size_check\" label in ea_get(), the code checks if the extended\nattribute list (xattr) size matches ea_size. If not, it logs\n\"ea_get: invalid extended attribute\" and calls print_hex_dump().\n\nHere, EALIST_SIZE(ea_buf->xattr) returns 4110417968, which exceeds\nINT_MAX (2,147,483,647). Then ea_size is clamped:\n\n\tint size = clamp_t(int, ea_size, 0, EALIST_SIZE(ea_buf->xattr));\n\nAlthough clamp_t aims to bound ea_size between 0 and 4110417968, the upper\nlimit is treated as an int, causing an overflow above 2^31 - 1. This leads\n\"size\" to wrap around and become negative (-184549328).\n\nThe \"size\" is then passed to print_hex_dump() (called \"len\" in\nprint_hex_dump()), it is passed as type size_t (an unsigned\ntype), this is then stored inside a variable called\n\"int remaining\", which is then assigned to \"int linelen\" which\nis then passed to hex_dump_to_buffer(). In print_hex_dump()\nthe for loop, iterates through 0 to len-1, where len is\n18446744073525002176, calling hex_dump_to_buffer()\non each iteration:\n\n\tfor (i = 0; i < len; i += rowsize) {\n\t\tlinelen = min(remaining, rowsize);\n\t\tremaining -= rowsize;\n\n\t\thex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,\n\t\t\t\t   linebuf, sizeof(linebuf), ascii);\n\n\t\t...\n\t}\n\nThe expected stopping condition (i < len) is effectively broken\nsince len is corrupted and very large. This eventually leads to\nthe \"ptr+i\" being passed to hex_dump_to_buffer() to get closer\nto the end of the actual bounds of \"ptr\", eventually an out of\nbounds access is done in hex_dump_to_buffer() in the following\nfor loop:\n\n\tfor (j = 0; j < len; j++) {\n\t\t\tif (linebuflen < lx + 2)\n\t\t\t\tgoto overflow2;\n\t\t\tch = ptr[j];\n\t\t...\n\t}\n\nTo fix this we should validate \"EALIST_SIZE(ea_buf->xattr)\"\nbefore it is utilised."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: jfs: corrección de lectura fuera de los límites de slab en ea_get(). Durante la etiqueta \"size_check\" en ea_get(), el código comprueba si el tamaño de la lista de atributos extendidos (xattr) coincide con ea_size. De lo contrario, registra \"ea_get: atributo extendido no válido\" y llama a print_hex_dump(). En este caso, EALIST_SIZE(ea_buf-&gt;xattr) devuelve 4110417968, que excede INT_MAX (2147483647). A continuación, se fija ea_size: int size = clamp_t(int, ea_size, 0, EALIST_SIZE(ea_buf-&gt;xattr)); Aunque clamp_t busca limitar ea_size entre 0 y 4110417968, el límite superior se trata como un entero, lo que provoca un desbordamiento por encima de 2^31 - 1. Esto hace que \"size\" se repita y se vuelva negativo (-184549328). El \"size\" se pasa a print_hex_dump() (llamado \"len\" en print_hex_dump()) como tipo size_t (un tipo sin signo). Este se almacena en una variable llamada \"int remaining\", que se asigna a \"int linelen\", que a su vez se pasa a hex_dump_to_buffer(). En print_hex_dump(), el bucle for itera desde 0 hasta len-1, donde len es 18446744073525002176 y llama a hex_dump_to_buffer() en cada iteración: for (i = 0; i &lt; len; i += rowsize) { linelen = min(remaining, rowsize); remaining -= rowsize; hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize, linebuf, sizeof(linebuf), ascii); ... } La condición de detención esperada (i &lt; len) se rompe efectivamente ya que len está dañado y es muy grande. Esto eventualmente lleva a que \"ptr+i\" se pase a hex_dump_to_buffer() para acercarse al final de los límites reales de \"ptr\", eventualmente se realiza un acceso fuera de los límites en hex_dump_to_buffer() en el siguiente bucle for: for (j = 0; j &lt; len; j++) { if (linebuflen &lt; lx + 2) goto overflow2; ch = ptr[j]; ... } Para solucionar esto debemos validar \"EALIST_SIZE(ea_buf-&gt;xattr)\" antes de utilizarlo."
    }
  ],
  "lastModified": "2026-06-17T09:18:22.470",
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}