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CVE-2026-93095
hfsplus: validate thread record before delete key rebuild
Published 2026-09-17 (31 days ago) by the Linux kernel CNA. Subsystem fs/hfsplus. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-93095 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
hfsplus_delete_cat() is called with str == NULL when the last open reference to an unlinked HFS+ hardlink backing inode is closed. In that case, the function finds the catalog thread by CNID and rebuilds the catalog key from thread.nodeName. That reconstruction path reads thread.nodeName.length directly from the catalog B-tree into fd.search_key and then copies length * 2 bytes into fd.search_key->cat.name.unicode. It does not first check that the found record is a thread record or that its size matches the thread name. A corrupted image can therefore provide an oversized thread name length and make hfs_bnode_read() write past the catalog search-key allocation. Read the CNID record through hfsplus_brec_read_cat(), which bounds the record read to sizeof(hfsplus_cat_entry) and verifies that a thread record's size exactly matches nodeName.length. Together, these checks ensure an accepted thread name fits HFSPLUS_MAX_STRLEN. Reject non-thread records before building the delete key from the validated thread name. Share the thread-record-type helper between hfsplus_find_cat() and hfsplus_delete_cat().
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.
fs/hfsplus/catalog.c
fs/hfsplus/hfsplus_fs.h
- What this is
- HFSPLUS FILESYSTEMMAINTAINERS section matched on fs/hfsplus/ · linux-fsdevel@vger.kernel.org · Maintained
- Kernel module
- hfsplus
Check it on the machine
grep -w CONFIG_HFSPLUS_FS /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.
lsmod | grep -w hfsplusPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_HFSPLUS_FS
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
- 2026-09-17 (31 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
- 0.18%, higher than 6.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/hfsplus
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.12 | 5.10.270 | 33cda0036bc6 |
| 2.6.12 | 5.15.221 | b9729c51a8b6 |
| 2.6.12 | 6.1.188 | af48abc1b00d |
| 2.6.12 | 6.6.157 | e20f3b749ad2 |
| 2.6.12 | 6.12.110 | 7898beee166c |
| 2.6.12 | 6.18.52 | e31985c67ba0 |
| 2.6.12 | 7.2.6 | 473ea7aa3561 |
| 2.6.12 | 7.3 | e2ea5cac61ac |
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:LAttack vector, local
- The malformed value is on-disk catalog thread.nodeName.length. unlink(2) reaches it via do_unlinkat → vfs_unlink → hfsplus_unlink, and close via hfsplus_file_release; both call hfsplus_delete_cat() with str==NULL so hfs_bnode_read() copies that length into fd.search_key. This is local block/loop/USB VFS data, not a ksmbd/nfsd/packet field.
- AC:LAttack complexity, low
- A crafted HFS+ catalog thread with nodeName.length above HFSPLUS_MAX_STRLEN (255) makes hfs_bnode_read() write length*2 bytes into fd.search_key->cat.name.unicode, which hfs_find_init() allocated as only cat_tree->max_key_len*2+4 bytes (~1036). The overflow is deterministic on unlink/close of that hardlink backing inode; no race or uninfluenced layout is required.
- PR:LPrivileges required, low
- hfsplus_fs_type is FS_REQUIRES_DEV without FS_USERNS_MOUNT, so raw mount(2) needs CAP_SYS_ADMIN, but the highest-impact case is an unprivileged user whose USB/loop HFS+ image is mounted by udisks2/polkit or a desktop automounter. After mount, may_delete_dentry only requires MAY_WRITE|MAY_EXEC on the attacker-owned directory.
- UI:NUser interaction, none
- The attacker supplies the crafted volume and then issues unlink(2) or close on the hardlink themselves. Automount of that local/removable image is not a separate victim action once the vector is Local.
- S:UScope, unchanged
- The hfs_find_init() kmalloc overflow and any resulting kernel memory corruption stay inside the host kernel that is parsing the HFS+ catalog B-tree. No KVM/Xen guest-to-host, IOMMU, or sandbox boundary is crossed.
- C:HConfidentiality impact, high
- hfs_bnode_read() copies attacker-chosen catalog bytes past the search-key object into adjacent heap. That out-of-bounds write is a memory-corruption primitive that can be leveraged for arbitrary kernel-memory disclosure.
- I:HIntegrity impact, high
- The same unbounded write from hfs_bnode_read() into the hfs_find_init() search-key allocation overwrites neighboring slab objects, which is sufficient for an arbitrary kernel write and control-flow hijacking.
- A:HAvailability impact, high
- Writing past the ~1036-byte search-key object oopses or panics the kernel (slab-out-of-bounds or GP fault) while cat_tree->tree_lock is held, crashing the machine or wedging further HFS+ operations.