{"cve":"CVE-2026-74342","nvd":{"published":"2026-08-15T06:22:35.253","modified":"2026-08-17T06:19:28.763","status":"Received","description":"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).","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/319b82e8b46edaf557436ad858e734e583f78ec9","https://git.kernel.org/stable/c/6cccc49b027c7551ffc1d2532f2ef1922661f3da"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:48:17.459049833+00:00"},"epss":{"cve":"CVE-2026-74342","score":0.00198,"percentile":0.09566,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}