CVE-2021-47636
Estado: ModificadaAlta (7.1)—
In the Linux kernel, the following vulnerability has been resolved:
ubifs: Fix read out-of-bounds in ubifs_wbuf_write_nolock()
Function ubifs_wbuf_write_nolock() may access buf out of bounds in following process:
Function ubifs_wbuf_write_nolock() accepts that parameter 'len' is not 8 bytes aligned, the 'len' represents the true length of buf (which is allocated in 'ubifs_jnl_xxx', eg. ubifs_jnl_write_inode), so ubifs_wbuf_write_nolock() must handle the length read from 'buf' carefully to write leb safely.
Fetch a reproducer in [Link].
Detalles técnicos trazas, registros y código del informe original
ubifs_wbuf_write_nolock():
aligned_len = ALIGN(len, 8); // Assume len = 4089, aligned_len = 4096
if (aligned_len <= wbuf->avail) ... // Not satisfy
if (wbuf->used) {
ubifs_leb_write() // Fill some data in avail wbuf
len -= wbuf->avail; // len is still not 8-bytes aligned
aligned_len -= wbuf->avail;
}
n = aligned_len >> c->max_write_shift;
if (n) {
n <<= c->max_write_shift;
err = ubifs_leb_write(c, wbuf->lnum, buf + written,
wbuf->offs, n);
// n > len, read out of bounds less than 8(n-len) bytes
}
, which can be catched by KASAN:
=========================================================
BUG: KASAN: slab-out-of-bounds in ecc_sw_hamming_calculate+0x1dc/0x7d0
Read of size 4 at addr ffff888105594ff8 by task kworker/u8:4/128
Workqueue: writeback wb_workfn (flush-ubifs_0_0)
Call Trace:
kasan_report.cold+0x81/0x165
nand_write_page_swecc+0xa9/0x160
ubifs_leb_write+0xf2/0x1b0 [ubifs]
ubifs_wbuf_write_nolock+0x421/0x12c0 [ubifs]
write_head+0xdc/0x1c0 [ubifs]
ubifs_jnl_write_inode+0x627/0x960 [ubifs]
wb_workfn+0x8af/0xb80CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- Puntuación base: 7.1
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.25%
- Percentil entre todas las CVEs puntuadas: 15
- Fecha de la puntuación: 5/10/2026
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.
- Explotación
T1068Exploitation for Privilege Escalationprivilege escalation85 % - Impacto principal
T1059Command and Scripting Interpreterexecution60 % - Impacto secundario
T1499.004Application or System Exploitationimpact70 %
AV:L/PR:L sin UI indica escalada local; la lectura fuera de límites (CWE-125) en ubifs_wbuf_write_nolock() puede causar corrupción de memoria, permitiendo ejecución de código o denegación de servicio en el kernel de Linux.
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
Tecnologías afectadas (1)
CWE
- CWE-125
- CWE-125
Referencias
- https://git.kernel.org/stable/c/07a209fadee7b53b46858538e1177597273862e4
- https://git.kernel.org/stable/c/3b7fb89135a20587d57f8877c02e25003e9edbdf
- https://git.kernel.org/stable/c/4f2262a334641e05f645364d5ade1f565c85f20b
- https://git.kernel.org/stable/c/5343575aa11c5d7044107d59d43f84aec01312b0
- https://git.kernel.org/stable/c/a7054aaf1909cf40489c0ec1b728fdcf79c751a6
- https://git.kernel.org/stable/c/b80ccbec0e4804436c382d7dd60e943c386ed83a
- https://git.kernel.org/stable/c/e09fa5318d51f522e1af4fbaf8f74999355980c8
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nubifs: Fix read out-of-bounds in ubifs_wbuf_write_nolock()\n\nFunction ubifs_wbuf_write_nolock() may access buf out of bounds in\nfollowing process:\n\nubifs_wbuf_write_nolock():\n aligned_len = ALIGN(len, 8); // Assume len = 4089, aligned_len = 4096\n if (aligned_len <= wbuf->avail) ... // Not satisfy\n if (wbuf->used) {\n ubifs_leb_write() // Fill some data in avail wbuf\n len -= wbuf->avail; // len is still not 8-bytes aligned\n aligned_len -= wbuf->avail;\n }\n n = aligned_len >> c->max_write_shift;\n if (n) {\n n <<= c->max_write_shift;\n err = ubifs_leb_write(c, wbuf->lnum, buf + written,\n wbuf->offs, n);\n // n > len, read out of bounds less than 8(n-len) bytes\n }\n\n, which can be catched by KASAN:\n =========================================================\n BUG: KASAN: slab-out-of-bounds in ecc_sw_hamming_calculate+0x1dc/0x7d0\n Read of size 4 at addr ffff888105594ff8 by task kworker/u8:4/128\n Workqueue: writeback wb_workfn (flush-ubifs_0_0)\n Call Trace:\n kasan_report.cold+0x81/0x165\n nand_write_page_swecc+0xa9/0x160\n ubifs_leb_write+0xf2/0x1b0 [ubifs]\n ubifs_wbuf_write_nolock+0x421/0x12c0 [ubifs]\n write_head+0xdc/0x1c0 [ubifs]\n ubifs_jnl_write_inode+0x627/0x960 [ubifs]\n wb_workfn+0x8af/0xb80\n\nFunction ubifs_wbuf_write_nolock() accepts that parameter 'len' is not 8\nbytes aligned, the 'len' represents the true length of buf (which is\nallocated in 'ubifs_jnl_xxx', eg. ubifs_jnl_write_inode), so\nubifs_wbuf_write_nolock() must handle the length read from 'buf' carefully\nto write leb safely.\n\nFetch a reproducer in [Link]."
},
{
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"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: ubifs: Se corrige la lectura fuera de los límites en la función ubifs_wbuf_write_nolock() ubifs_wbuf_write_nolock() puede acceder a buf fuera de los límites en el siguiente proceso: ubifs_wbuf_write_nolock(): classified_len = ALIGN(len, 8); // Supongamos que len = 4089, classified_len = 4096 if (aligned_len <= wbuf->avail) ... // No satisface if (wbuf->used) { ubifs_leb_write() // Complete algunos datos en avail wbuf len -= wbuf->avail; // len aún no está alineado a 8 bytes classified_len -= wbuf->avail; } n = classified_len >> c->max_write_shift; if (n) { n <<= c->max_write_shift; err = ubifs_leb_write(c, wbuf->lnum, buf + escrito, wbuf->offs, n); // n > len, lectura fuera de los límites menor a 8(n-len) bytes }, lo cual puede ser detectado por KASAN: =========================================================== ERROR: KASAN: slab fuera de los límites en ecc_sw_hamming_calculate+0x1dc/0x7d0 Lectura de tamaño 4 en la dirección ffff888105594ff8 por la tarea kworker/u8:4/128 Cola de trabajo: escritura diferida wb_workfn (flush-ubifs_0_0) Rastreo de llamadas: kasan_report.cold+0x81/0x165 nand_write_page_swecc+0xa9/0x160 ubifs_leb_write+0xf2/0x1b0 [ubifs] ubifs_wbuf_write_nolock+0x421/0x12c0 [ubifs] write_head+0xdc/0x1c0 [ubifs] ubifs_jnl_write_inode+0x627/0x960 [ubifs] wb_workfn+0x8af/0xb80 La función ubifs_wbuf_write_nolock() acepta que el parámetro 'len' no esté alineado con 8 bytes, 'len' representa la longitud verdadera de buf (que está asignada en 'ubifs_jnl_xxx', p. ej. ubifs_jnl_write_inode), por lo que ubifs_wbuf_write_nolock() debe manejar la longitud leída de 'buf' con cuidado para escribir leb de forma segura. Obtenga un reproductor en [Enlace]."
}
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"lastModified": "2026-06-17T04:18:12.480",
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