CVE-2026-43071
Estado: ModificadaCrítica (9.1)—
In the Linux kernel, the following vulnerability has been resolved:
dcache: Limit the minimal number of bucket to two
Fix it by limiting the minimal number of dentry_hashtable bucket to two, so that 'd_hash_shift' won't exceeds the bit width of type u32.
Detalles técnicos trazas, registros y código del informe original
There is an OOB read problem on dentry_hashtable when user sets
'dhash_entries=1':
BUG: unable to handle page fault for address: ffff888b30b774b0
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
Oops: Oops: 0000 [#1] SMP PTI
RIP: 0010:__d_lookup+0x56/0x120
Call Trace:
d_lookup.cold+0x16/0x5d
lookup_dcache+0x27/0xf0
lookup_one_qstr_excl+0x2a/0x180
start_dirop+0x55/0xa0
simple_start_creating+0x8d/0xa0
debugfs_start_creating+0x8c/0x180
debugfs_create_dir+0x1d/0x1c0
pinctrl_init+0x6d/0x140
do_one_initcall+0x6d/0x3d0
kernel_init_freeable+0x39f/0x460
kernel_init+0x2a/0x260
There will be only one bucket in dentry_hashtable when dhash_entries is
set as one, and d_hash_shift is calculated as 32 by dcache_init(). Then,
following process will access more than one buckets(which memory region
is not allocated) in dentry_hashtable:
d_lookup
b = d_hash(hash)
dentry_hashtable + ((u32)hashlen >> d_hash_shift)
// The C standard defines the behavior of right shift amounts
// exceeding the bit width of the operand as undefined. The
// result of '(u32)hashlen >> d_hash_shift' becomes 'hashlen',
// so 'b' will point to an unallocated memory region.
hlist_bl_for_each_entry_rcu(b)
hlist_bl_first_rcu(head)
h->first // read OOB!CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- Puntuación base: 9.1
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.73%
- Percentil entre todas las CVEs puntuadas: 53
- 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
T1190Exploit Public-Facing Applicationinitial access45 % - Impacto principal
T1499.004Application or System Exploitationimpact70 %
OOB read en kernel Linux por dhash_entries=1 causa DoS por panic. Acceso remoto sin privilegios (AV:N/AC:L/PR:N) permite causar denegación de servicio; lectura de memoria kernel no confirmada explícitamente.
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
Referencias
- https://git.kernel.org/stable/c/277cedabb0ab86baae83fa58218be13c6d3e5526
- https://git.kernel.org/stable/c/426ef05e82ee52c8d0e95fc0808b7383d8352d73
- https://git.kernel.org/stable/c/45b06bb5ea96f75ad81d7ef446f832ea6b0026fe
- https://git.kernel.org/stable/c/5718df131ab78897a9dd1f2e71c3ba732d4392af
- https://git.kernel.org/stable/c/755b40903eff563768d4d96fd4ef51ec48adde3b
- https://git.kernel.org/stable/c/ddd57ebce245f9c7e2f6902a6c087d6186d2385d
- https://git.kernel.org/stable/c/f08fe8891c3eeb63b73f9f1f6d97aa629c821579
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndcache: Limit the minimal number of bucket to two\n\nThere is an OOB read problem on dentry_hashtable when user sets\n'dhash_entries=1':\n BUG: unable to handle page fault for address: ffff888b30b774b0\n #PF: supervisor read access in kernel mode\n #PF: error_code(0x0000) - not-present page\n Oops: Oops: 0000 [#1] SMP PTI\n RIP: 0010:__d_lookup+0x56/0x120\n Call Trace:\n d_lookup.cold+0x16/0x5d\n lookup_dcache+0x27/0xf0\n lookup_one_qstr_excl+0x2a/0x180\n start_dirop+0x55/0xa0\n simple_start_creating+0x8d/0xa0\n debugfs_start_creating+0x8c/0x180\n debugfs_create_dir+0x1d/0x1c0\n pinctrl_init+0x6d/0x140\n do_one_initcall+0x6d/0x3d0\n kernel_init_freeable+0x39f/0x460\n kernel_init+0x2a/0x260\n\nThere will be only one bucket in dentry_hashtable when dhash_entries is\nset as one, and d_hash_shift is calculated as 32 by dcache_init(). Then,\nfollowing process will access more than one buckets(which memory region\nis not allocated) in dentry_hashtable:\n d_lookup\n b = d_hash(hash)\n dentry_hashtable + ((u32)hashlen >> d_hash_shift)\n // The C standard defines the behavior of right shift amounts\n // exceeding the bit width of the operand as undefined. The\n // result of '(u32)hashlen >> d_hash_shift' becomes 'hashlen',\n // so 'b' will point to an unallocated memory region.\n hlist_bl_for_each_entry_rcu(b)\n hlist_bl_first_rcu(head)\n h->first // read OOB!\n\nFix it by limiting the minimal number of dentry_hashtable bucket to two,\nso that 'd_hash_shift' won't exceeds the bit width of type u32."
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