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CVE-2026-90419
nilfs2: prevent out-of-bounds read in super root block parsing
Published 2026-09-17 (31 days ago) by the Linux kernel CNA. Subsystem fs/nilfs2. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-90419 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
super-root inode metadata size is trusted before nilfs_read_inode_common(). Reject super-root inode sizes whose computed on-disk footprint exceeds the filesystem block size. This prevents malformed filesystem images from making nilfs_read_inode_common() read past the end of the super-root block. [ryusuke: clarify the commit title]
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/nilfs2/the_nilfs.c
- What this is
- NILFS2 FILESYSTEMMAINTAINERS section matched on fs/nilfs2/ · linux-nilfs@vger.kernel.org · Maintained
- Kernel module
- nilfs2
Check it on the machine
grep -w CONFIG_NILFS2_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 nilfs2Prints 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_NILFS2_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
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/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/nilfs2
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.30 | 5.10.270 | 16df25205028 |
| 2.6.30 | 5.15.221 | dcc85fc28f88 |
| 2.6.30 | 6.1.188 | 5b69ebe20d7f |
| 2.6.30 | 6.6.157 | 7029e70cf86d |
| 2.6.30 | 6.12.110 | 71bd64471ff5 |
| 2.6.30 | 6.18.52 | 842397fdfd2e |
| 2.6.30 | 7.2.6 | 15c855937641 |
| 2.6.30 | 7.3 | 7cb2f76a6a2b |
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 oversized s_inode_size is on-disk in the nilfs2 superblock; nilfs_store_disk_layout() stores it and nilfs_load_super_root() indexes the super-root buffer with NILFS_SR_CPFILE_OFFSET during local mount (nilfs_get_tree → nilfs_fill_super → init_nilfs/load_nilfs). No network protocol carries s_inode_size.
- AC:LAttack complexity, low
- A crafted s_inode_size that still passes ns_inode_size <= ns_blocksize but makes NILFS_SR_BYTES(inode_size) exceed ns_blocksize (for example inode_size == blocksize) puts NILFS_SR_CPFILE_OFFSET/SUFILE_OFFSET past bh_sr->b_data, so nilfs_read_inode_common() over-reads on every mount of that image. There is no race.
- PR:NPrivileges required, none
- Crafting the image needs no host account. nilfs_fs_type.fs_flags is only FS_REQUIRES_DEV (no FS_USERNS_MOUNT), so mount_capable() requires init-namespace CAP_SYS_ADMIN; that privileged mount is the victim's action and is scored as UI:R, not attacker privilege.
- UI:RUser interaction, required
- The over-read runs only in nilfs_load_super_root() from nilfs_fill_super() after a victim or automounter mounts the attacker-supplied nilfs2 image via mount/fsopen. That mount is the required user interaction.
- S:UScope, unchanged
- nilfs_read_inode_common()'s over-read of the super-root buffer_head stays in the host kernel mount path and does not cross a VM, IOMMU, or sandbox authority.
- C:HConfidentiality impact, high
- With inode_size == ns_blocksize, NILFS_SR_CPFILE_OFFSET is 16 bytes past the super-root block, and nilfs_read_inode_common() loads a full 128-byte struct nilfs_inode (including a 56-byte i_bmap memcpy in nilfs_bmap_read) from that address. That is not a few-byte leak.
- I:NIntegrity impact, none
- The defect is a source over-read into in-bounds VFS inode and bmap fields; there is no store through the out-of-bounds pointer and no OOB write. Leaked i_bmap words are used only as on-disk block numbers, not as a kernel write primitive.
- A:HAvailability impact, high
- A 4K block with inode_size == 4096 places the cpfile inode 16 bytes past the page-backed super-root buffer, so the 128-byte load can fault on an unmapped next linear-map page (KASAN, debug_pagealloc, page poisoning) and oops the mounting kernel.