CVE-2025-39817
Estado: ModificadaAlta (7.1)—
In the Linux kernel, the following vulnerability has been resolved:
efivarfs: Fix slab-out-of-bounds in efivarfs_d_compare
Observed on kernel 6.6 (present on master as well):
If dentry->d_name.len < EFI_VARIABLE_GUID_LEN , 'guid' can become negative, leadings to oob. The issue can be triggered by parallel lookups using invalid filename:
lookup_open d_alloc_parallel __d_lookup_rcu __d_lookup_rcu_op_compare hlist_bl_for_each_entry_rcu // invalid dentry can be retrieved ->d_compare efivarfs_d_compare // oob
Fix it by checking 'guid' before cmp.
Detalles técnicos trazas, registros y código del informe original
BUG: KASAN: slab-out-of-bounds in memcmp+0x98/0xd0
Call trace:
kasan_check_range+0xe8/0x190
__asan_loadN+0x1c/0x28
memcmp+0x98/0xd0
efivarfs_d_compare+0x68/0xd8
__d_lookup_rcu_op_compare+0x178/0x218
__d_lookup_rcu+0x1f8/0x228
d_alloc_parallel+0x150/0x648
lookup_open.isra.0+0x5f0/0x8d0
open_last_lookups+0x264/0x828
path_openat+0x130/0x3f8
do_filp_open+0x114/0x248
do_sys_openat2+0x340/0x3c0
__arm64_sys_openat+0x120/0x1a0
T1 T2
lookup_open
->lookup
simple_lookup
d_add
// invalid dentry is added to hash listCVSS
- 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: 0.16%
- Percentil entre todas las CVEs puntuadas: 5
- 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 escalation75 % - Impacto principal
T1059Command and Scripting Interpreterexecution45 % - Impacto secundario
T1499.004Application or System Exploitationimpact65 %
AV:L, PR:L, sin UI: escalada de privilegios local. KASAN slab-out-of-bounds en memcmp permite lectura/escritura de memoria kernel (I:N sugiere DoS por corrupción). Ejecución de código es especulativa sin PoC explícito.
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 (2)
CWE
- CWE-125
Referencias
- https://git.kernel.org/stable/c/0f63fbabeaaaaaaf5b742a2f4c1b4590d50bf1f6
- https://git.kernel.org/stable/c/568e7761279b99c6daa3002290fd6d8047ddb6d2
- https://git.kernel.org/stable/c/71581a82f38e5a4d807d71fc1bb59aead80ccf95
- https://git.kernel.org/stable/c/794399019301944fd6d2e0d7a51b3327e26c410e
- https://git.kernel.org/stable/c/925599eba46045930b850a98ae594d2e3028ac40
- https://git.kernel.org/stable/c/a6358f8cf64850f3f27857b8ed8c1b08cfc4685c
- https://git.kernel.org/stable/c/c2925cd6207079c3f4d040d082515db78d63afbf
- https://git.kernel.org/stable/c/d7f5e35e70507d10cbaff5f9e194ed54c4ee14f7
- https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
- https://cert-portal.siemens.com/productcert/html/ssa-032379.html
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nefivarfs: Fix slab-out-of-bounds in efivarfs_d_compare\n\nObserved on kernel 6.6 (present on master as well):\n\n BUG: KASAN: slab-out-of-bounds in memcmp+0x98/0xd0\n Call trace:\n kasan_check_range+0xe8/0x190\n __asan_loadN+0x1c/0x28\n memcmp+0x98/0xd0\n efivarfs_d_compare+0x68/0xd8\n __d_lookup_rcu_op_compare+0x178/0x218\n __d_lookup_rcu+0x1f8/0x228\n d_alloc_parallel+0x150/0x648\n lookup_open.isra.0+0x5f0/0x8d0\n open_last_lookups+0x264/0x828\n path_openat+0x130/0x3f8\n do_filp_open+0x114/0x248\n do_sys_openat2+0x340/0x3c0\n __arm64_sys_openat+0x120/0x1a0\n\nIf dentry->d_name.len < EFI_VARIABLE_GUID_LEN , 'guid' can become\nnegative, leadings to oob. The issue can be triggered by parallel\nlookups using invalid filename:\n\n T1\t\t\tT2\n lookup_open\n ->lookup\n simple_lookup\n d_add\n // invalid dentry is added to hash list\n\n\t\t\tlookup_open\n\t\t\t d_alloc_parallel\n\t\t\t __d_lookup_rcu\n\t\t\t __d_lookup_rcu_op_compare\n\t\t\t hlist_bl_for_each_entry_rcu\n\t\t\t // invalid dentry can be retrieved\n\t\t\t ->d_compare\n\t\t\t efivarfs_d_compare\n\t\t\t // oob\n\nFix it by checking 'guid' before cmp."
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