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CVE-2026-89643
audit: avoid dropping live tree ref on fsnotify rule autoremove
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem kernel. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89643 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 | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
audit_del_rule() is used for both netlink deletion templates and internal fsnotify autoremove. The former passes a parsed template which owns a temporary tree reference; the latter passes the installed entry itself. The unconditional audit_put_tree() at the end of audit_del_rule() assumes the template case. For mixed AUDIT_DIR plus AUDIT_EXE rules, an fsnotify autoremove event therefore drops the installed rule's live tree reference. Repeating this across rules sharing the same tree can free the tree while another rule still references it, and a later autoremove dereferences the freed pathname while comparing rules. Move the temporary-tree put to audit_rule_change(), the caller that owns deletion templates. Keep it in the AUDIT_DEL_RULE cleanup so both successful deletion and -ENOENT still release the parser-owned tree. [PM: dropped unnecessary comment for line length reasons]
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.
kernel/auditfilter.c
- What this is
- AUDIT SUBSYSTEMMAINTAINERS section matched on kernel/audit* · audit@vger.kernel.org · Supported
Check it on the machine
grep -w CONFIG_AUDIT /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, sid, bookworm · linux-6.12y
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_AUDIT
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
- 2026-09-11 (37 days ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.71%, higher than 52.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- kernel
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.3 | 5.10.270 | 9cac21f8eb82 |
| 4.3 | 5.15.221 | b322cc7adcd2 |
| 4.3 | 6.1.188 | 695c85dc345a |
| 4.3 | 6.6.157 | 01b0ec8c397b |
| 4.3 | 6.12.109 | cf37b61b5420 |
| 4.3 | 6.18.50 | 636a99bab36b |
| 4.3 | 7.2.4 | 583cf579b32d |
| 4.3 | 7.3 | 783f0f0974c1 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | 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:NAttack vector, network
- audit_autoremove_mark_rule() runs from fsnotify FS_MOVE_SELF/FS_DELETE_SELF/FS_UNMOUNT on the AUDIT_EXE parent directory; nfsd and ksmbd vfs_rename/vfs_rmdir of that directory reach the same path over the network, not only local renameat/rmdir.
- AC:LAttack complexity, low
- Each EXE fsnotify autoremove deterministically extra-puts the live shared audit_tree; the attacker issues sequential directory renames/rmdirs they fully control and needs no race or memory layout beyond their influence.
- PR:NPrivileges required, none
- Triggering requires only renaming or rmdir'ing the parent directory of an audited executable on a local or NFS/SMB-exported path; a remote client needs no local account, CAP_AUDIT_CONTROL, or init-namespace root beyond export write access.
- UI:NUser interaction, none
- The attacker triggers autoremove with their own rename/rmdir (local or via nfsd/ksmbd); no other user must open files, mount a filesystem, or otherwise interact.
- S:UScope, unchanged
- The use-after-free corrupts host kernel heap (struct audit_tree) and stays within the same kernel security authority; it is not a VM escape, IOMMU bypass, or other documented cross-boundary impact.
- C:HConfidentiality impact, high
- Use-after-free of the shared audit_tree lets a later audit_compare_rule() strcmp the freed pathname and remaining rules dereference attacker-reclaimed tree objects, enabling arbitrary kernel reads.
- I:HIntegrity impact, high
- The dangling tree is then used in audit_remove_tree_rule() list_del/list_move and prune_one() after extra puts free it, enabling heap spraying, list corruption, arbitrary writes, and control-flow hijack.
- A:HAvailability impact, high
- Dereferencing the freed audit_tree pathname or underflowing its refcount during prune oopses/panics the kernel; the UAF can be triggered repeatedly for denial of service.