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VulnerabilityPublished Updated

CVE-2026-74342: Linux kernel · kernfs: link kn to its parent before the LSM init hook

Affects Linux kernelSource GCVE Database

0

Not known to be exploited · CVSS 5.7 Medium.

Data as of 28 Oct 2026, 00:59 UTC

CVSS 4.0 base score
5.7Medium
How severe the flaw is on the 0–10 CVSS scale.
CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 15 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Ubuntu 26.10linuxpkg:deb/ubuntu/linux?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-14.14 – 7.3.0-9.9
6 affected builds
Fixed in–
Ubuntu 26.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1004.4 – 7.3.0-1003.3
5 affected builds
Fixed in–
Ubuntu 26.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1004.4 – 7.3.0-1003.3
5 affected builds
Fixed in–
Ubuntu 26.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=stonkingOther threatsAffected
  • =7.0.0-1004.4
  • =7.3.0-1002.3
  • =7.3.0-1003.4
Fixed in–
Ubuntu 26.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1003.3 – 7.3.0-1003.3
5 affected builds
Fixed in–
Ubuntu 26.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=stonkingOther threatsAffected
  • 7.0.0-1003.3 – 7.3.0-1003.3
5 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

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: 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 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).

References

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