CVE-2026-74342
In the Linux kernel, the following vulnerability has been resolved:
kernfs: link kn to its parent before the LSM init hook
After commit 12e9e3cd03b5 ("simpe_xattr: use per-sb cache"), kernfs_xattr_set() and kernfs_xattr_get() compute the cache via kernfs_root(kn) before any other check. kernfs_root(kn) walks kn->__parent first and falls back to kn->dir.root, both of which are NULL on a freshly kmem_cache_zalloc()'d kn. kn->__parent was being set in kernfs_new_node() after __kernfs_new_node() returned, and kn->dir.root is set even later by kernfs_create_dir_ns() / kernfs_create_empty_dir().
The LSM kernfs_init_security hook is invoked from inside __kernfs_new_node(), before either field has been initialized. selinux_kernfs_init_security() ends with kernfs_xattr_set(kn, XATTR_NAME_SELINUX, ...). kernfs_root(kn) then returns NULL, and &((struct kernfs_root *)NULL)->xa_cache evaluates to offsetof(struct kernfs_root, xa_cache) which faults:
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Reproduces deterministically at PID 1 (systemd) on an SELinux-enabled distro. The first cgroup mkdir under /sys/fs/cgroup with a labelled parent panics the kernel.
The LSM hook's contract is that the kn_dir argument is the parent of the new kn, so kn->__parent should already point at kn_dir when the hook runs. Move kernfs_get(parent) and rcu_assign_pointer of kn->__parent from kernfs_new_node() into __kernfs_new_node() right before the security hook, and unwind the parent reference on the err_out4 path. kernfs_root(kn) then takes its parent branch during the hook and returns parent->dir.root, which is the correct root.
This also closes the same-shape latent bug in kernfs_xattr_get() (which today is hidden only by kernfs_iattrs_noalloc() returning NULL on a fresh kn).
Detalles técnicos trazas, registros y código del informe original
BUG: kernel NULL pointer dereference, address: 00000000000000e0 RIP: 0010:simple_xattr_set+0x27/0x8b0 Call Trace: kernfs_xattr_set+0x63/0xb0 selinux_kernfs_init_security+0x13b/0x270 security_kernfs_init_security+0x36/0xc0 __kernfs_new_node+0x182/0x290 kernfs_new_node+0x80/0xc0 kernfs_create_dir_ns+0x2b/0xa0 cgroup_create+0x116/0x380 cgroup_mkdir+0x7c/0x1a0
CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.20%
- Percentil entre todas las CVEs puntuadas: 9
- Fecha de la puntuación: 6/10/2026
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).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
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{
"id": "CVE-2026-74342",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"lessThan": "319b82e8b46edaf557436ad858e734e583f78ec9",
"versionType": "git"
},
{
"status": "affected",
"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
"lessThan": "6cccc49b027c7551ffc1d2532f2ef1922661f3da",
"versionType": "git"
},
{
"status": "affected",
"version": "0",
"lessThan": "7.1.5",
"versionType": "semver"
}
],
"programFiles": [
"fs/kernfs/dir.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "unaffected",
"version": "7.1.5",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/kernfs/dir.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-08-15T06:22:35.253",
"references": [
{
"url": "https://git.kernel.org/stable/c/319b82e8b46edaf557436ad858e734e583f78ec9",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/6cccc49b027c7551ffc1d2532f2ef1922661f3da",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nkernfs: link kn to its parent before the LSM init hook\n\nAfter commit 12e9e3cd03b5 (\"simpe_xattr: use per-sb cache\"),\nkernfs_xattr_set() and kernfs_xattr_get() compute the cache via\nkernfs_root(kn) before any other check. kernfs_root(kn) walks\nkn->__parent first and falls back to kn->dir.root, both of which are\nNULL on a freshly kmem_cache_zalloc()'d kn. kn->__parent was being set\nin kernfs_new_node() after __kernfs_new_node() returned, and kn->dir.root\nis set even later by kernfs_create_dir_ns() / kernfs_create_empty_dir().\n\nThe LSM kernfs_init_security hook is invoked from inside\n__kernfs_new_node(), before either field has been initialized.\nselinux_kernfs_init_security() ends with kernfs_xattr_set(kn,\nXATTR_NAME_SELINUX, ...). kernfs_root(kn) then returns NULL, and\n&((struct kernfs_root *)NULL)->xa_cache evaluates to\noffsetof(struct kernfs_root, xa_cache) which faults:\n\n BUG: kernel NULL pointer dereference, address: 00000000000000e0\n RIP: 0010:simple_xattr_set+0x27/0x8b0\n Call Trace:\n kernfs_xattr_set+0x63/0xb0\n selinux_kernfs_init_security+0x13b/0x270\n security_kernfs_init_security+0x36/0xc0\n __kernfs_new_node+0x182/0x290\n kernfs_new_node+0x80/0xc0\n kernfs_create_dir_ns+0x2b/0xa0\n cgroup_create+0x116/0x380\n cgroup_mkdir+0x7c/0x1a0\n\nReproduces deterministically at PID 1 (systemd) on an SELinux-enabled\ndistro. The first cgroup mkdir under /sys/fs/cgroup with a labelled\nparent panics the kernel.\n\nThe LSM hook's contract is that the kn_dir argument is the parent of\nthe new kn, so kn->__parent should already point at kn_dir when the\nhook runs. Move kernfs_get(parent) and rcu_assign_pointer of\nkn->__parent from kernfs_new_node() into __kernfs_new_node() right\nbefore the security hook, and unwind the parent reference on the\nerr_out4 path. kernfs_root(kn) then takes its parent branch during\nthe hook and returns parent->dir.root, which is the correct root.\n\nThis also closes the same-shape latent bug in kernfs_xattr_get() (which\ntoday is hidden only by kernfs_iattrs_noalloc() returning NULL on a\nfresh kn)."
}
],
"lastModified": "2026-08-17T06:19:28.763",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}