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CVE-2026-89838
f2fs: limit recovery filename logging to stored length
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem fs/f2fs. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89838 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 | 7.2.6-1 | 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. |
The vulnerability
What the bug is
F2FS stores recovery filenames as a length plus a fixed-size i_name buffer. The buffer is not NUL-terminated, but recover_inode() and recover_dentry() print it with %s. For a 255-byte filename, recovery logging can read past i_name into the following raw inode fields. Print the name with a precision bounded by i_namelen and F2FS_NAME_LEN.
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/f2fs/recovery.c
- What this is
- F2FS FILE SYSTEMMAINTAINERS section matched on fs/f2fs/ · linux-f2fs-devel@lists.sourceforge.net · Maintained
- Kernel module
- f2fs
Check it on the machine
grep -w CONFIG_F2FS_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 f2fsPrints 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, sidMnot 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_F2FS_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
- 2026-09-16 (33 days ago)source
- CVSS
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/f2fs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.11 | 6.12.112 | 7ab178007494 |
| 3.11 | 6.18.53 | 35c5abccd092 |
| 3.11 | 7.2.5 | 317d32e1a8de |
| 3.11 | 7.3 | 01027b2fcb74 |
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
- recover_inode() and recover_dentry() run only during local f2fs roll-forward in f2fs_fill_super() -> f2fs_recover_fsync_data(). This is a local block filesystem (Android userdata/portable storage), not a network protocol path such as ksmbd or nfsd.
- AC:LAttack complexity, low
- A crafted f2fs image with a 255-byte non-NUL i_name and a pending fsync node makes printk %s over-read deterministically on mount. Roll-forward is default-enabled; no race or attacker-uncontrollable layout is required.
- PR:LPrivileges required, low
- f2fs lacks FS_USERNS_MOUNT, but Android vold auto-mounts f2fs portable/adoptable storage and desktop/kiosk udisks2/polkit mounts removable media for an ordinary console user, so init-namespace root is not required.
- UI:NUser interaction, none
- The attacker supplies the crafted image; vold/udisks auto-mount runs roll-forward recovery without a separate deliberate victim mount or open. Recovery also fires automatically on the next mount after an unclean shutdown.
- S:UScope, unchanged
- The over-read and any resulting oops stay in the host kernel address space and security authority. This is not a VM escape, IOMMU bypass, or sandbox boundary crossing.
- C:HConfidentiality impact, high
- recover_inode()/recover_dentry() pass the 255-byte, non-NUL-terminated i_name to printk %s with no precision, so vsprintf scans past the field and the rest of the 4KB node folio into adjacent kernel memory and copies it into dmesg, an unbounded OOB read.
- I:NIntegrity impact, none
- The defect is a read-only printk over-read of i_name; it does not write kernel memory, corrupt adjacent objects, or provide a control-flow hijack primitive.
- A:HAvailability impact, high
- Unbounded %s scanning off the node folio can walk into unmapped pages or trip KASAN/page-poisoning and oops/panic the kernel during mount recovery, fully denying availability.