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CVE-2026-97594
landlock: Fix use-after-free of the source's parent directory
Published 2026-09-25 (24 days ago) by the Linux kernel CNA. Subsystem security/landlock. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-97594 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixedDSA-6568-1 · 2026-10-16 · text | 6.12.113-1 | Update the kernel and reboot. DSA-6568-1 shipped the fix on 2026-10-16, in 6.12.113-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.7-1 | Update the kernel and reboot. Fixed in 7.2.7-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.7-1 | Update the kernel and reboot. Fixed in 7.2.7-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
current_check_refer_path() reads old_dentry->d_parent without holding a reference nor a lock on it, and then dereferences it in collect_domain_accesses() and in the audit record. A reference on a child does not pin its parent: __d_move() reassigns dentry->d_parent and drops the reference the child held on its former parent. hook_path_rename() is not affected because the rename path calls lock_rename() before the hook, so the source cannot be reparented under it. hook_path_link() has no such protection: filename_linkat() holds a reference on the source dentry but neither locks nor references its parent, so a concurrent rename(2) can reparent the source while security_path_link() runs, and the former parent can then be removed and freed while the hook walks it. A process can trigger this after entering a Landlock domain that handles at least one filesystem access right. The process can then race a linkat(2) loop against rename(2) and rmdir(2): BUG: KASAN: slab-use-after-free in collect_domain_accesses+0x278/0x290 Read of size 4 at addr ffff888160bd53f4 by task llrepro2/549 collect_domain_accesses+0x278/0x290 current_check_refer_path+0x952/0x1120 security_path_link+0x1be/0x320 filename_linkat+0x342/0x6d0 __x64_sys_linkat+0xfa/0x150 Freed by task 562: kmem_cache_free+0x139/0x4c0 i_callback+0x4b/0x80 rcu_core+0x7dc/0x10a0 Take a reference on the dentry selected as the source parent, using dget() for the common-mount-root case and dget_parent() otherwise. Release it after the hierarchy walk and synchronous audit logging. [mic: Clarify the caller, reachability, and reference handling]
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
security/landlock/fs.c
- What this is
- LANDLOCK SECURITY MODULEMAINTAINERS section matched on security/landlock/ · linux-security-module@vger.kernel.org · Supported
Check it on the machine
grep -w CONFIG_SECURITY_LANDLOCK /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_SECURITY_LANDLOCK
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-25 (24 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.16%, higher than 4.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- security/landlock
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.19 | 6.12.112 | 4c37992b9668 |
| 5.19 | 6.18.53 | 379efd2ce8b2 |
| 5.19 | 7.2.7 | ba29c46ccfe3 |
| 5.19 | 7.3 | 2c6dc7925382 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DSA-6568-1 | 2026-10-16 | trixie 6.12.113-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The trigger is a local linkat(2) syscall: filename_linkat() -> security_path_link() -> hook_path_link() -> current_check_refer_path(), raced against local rename(2)/rmdir(2). No remote protocol supplies any of the input.
- AC:LAttack complexity, low
- The attacker runs every side of the race: a linkat() loop on their own file, plus rename() to reparent the source and rmdir() to free the old parent, all in directories they create (e.g. /tmp). No condition outside the attacker's control is needed; the window can be retried at will.
- PR:LPrivileges required, low
- An ordinary unprivileged user can enter a Landlock domain that handles any FS right (landlock_create_ruleset + landlock_restrict_self after PR_SET_NO_NEW_PRIVS, no capability needed); that makes landlock_get_applicable_subject() non-NULL and reaches the unpinned d_parent read.
- UI:NUser interaction, none
- The attacker's own syscalls on files and directories they own trigger the bug; no other user or administrator has to do anything.
- S:UScope, unchanged
- The corruption happens in kernel memory under the same kernel authority; exploiting it is standard local privilege escalation, not a crossing into a separate authority such as a hypervisor.
- C:HConfidentiality impact, high
- collect_domain_accesses() dereferences the freed old_parent dentry and follows its d_parent/d_inode pointers into the Landlock inode blob via find_rule(). If the attacker reallocates the freed slab, they control pointers that the kernel then follows and reads.
- I:HIntegrity impact, high
- collect_domain_accesses() calls dget() and later dput() on the freed dentry. That writes the lockref inside the freed or reallocated object and can run dentry teardown on it, a write primitive that can lead to a double free or control-flow hijack.
- A:HAvailability impact, high
- The KASAN report in the commit shows a slab use-after-free in collect_domain_accesses(). On production kernels the refcount changes on freed memory or the stale pointer walk can oops or panic the kernel.