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CVE-2026-89601
ext2: Fix lost inode updates for IS_SYNC inodes
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem fs/ext2. Debian urgency: not yet assigned.
Debian does not build this code. The per-release build detail is under "Where it lives" below.
What to do, per Debian release
Debian's own status for CVE-2026-89601 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 | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| 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
ext2_setsize() and ext2_xattr_set2() had a construct like: if (IS_SYNC(inode)) { sync_inode_metadata(inode, 1); } else { mark_inode_dirty(inode); } which leads to lost inode updates for IS_SYNC inodes because sync_inode_metadata() does anything only if the inode is already dirty and hence inode updates may be simply lost. Fix the problem by unconditionally marking the inode dirty and *then* call sync_inode_metadata().
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/ext2/inode.c
fs/ext2/xattr.c
- What this is
- EXT2 FILE SYSTEMMAINTAINERS section matched on fs/ext2/ · linux-ext4@vger.kernel.org · Maintained
- Kernel module
- none to look for. The file would have gone into ext2, and Debian does not compile it into that module, so finding ext2 in lsmod would say nothing about this CVE.
Check it on the machine
grep -w CONFIG_EXT2_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.
Show whether Debian builds this, per release
Debian does not build this code. In 4 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.
- bookworm, trixie, forky, sidn
- n
- not enabled on any flavour - this release does not build the code
- Build switch
- CONFIG_EXT2_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
- 2026-09-11 (37 days ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.58%, higher than 46.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/ext2
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 | 6.18.57 | 548176612504 |
| 2.6.12 | 7.2.4 | 5efb3350230f |
| 2.6.12 | 7.3 | 356984d1a5c3 |
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
- nfsd SETATTR/SETXATTR and ksmbd truncate/EA handling call notify_change()/vfs_setxattr() into ext2_setattr()/ext2_xattr_set2() when an ext2 volume is NFS/SMB-exported (NAS and embedded USB-storage appliances, including sync-mounted disks); a remote client with write access therefore reaches the lost IS_SYNC inode update without a local shell.
- AC:LAttack complexity, low
- The attacker can put the target in the IS_SYNC state at will (owner-writable FS_IOC_SETFLAGS/chattr +S, or a sync-mounted export) and then deterministically truncate or set/remove xattrs; sync_inode_metadata() skips a clean inode every time, with no race or memory layout outside attacker control.
- PR:LPrivileges required, low
- The path is gated only by ordinary VFS write checks (inode_permission MAY_WRITE, xattr_permission for user.* xattrs, or inode_owner_or_capable() for FS_IOC_SETFLAGS); an unprivileged local user or a low-privilege NFS/SMB client with write access to a file suffices, and no init-namespace capability is required.
- UI:NUser interaction, none
- The attacker performs every step themselves (setting the SYNC flag, truncating or changing xattrs/ACLs, and driving inode reclaim); no separate victim action such as mounting a crafted image is required.
- S:UScope, unchanged
- Impact is confined to filesystem metadata and file data on the host that mounted the ext2 volume; this is not a VM escape, IOMMU bypass, or other cross-authority boundary.
- C:HConfidentiality impact, high
- Removing the last xattr on an IS_SYNC inode frees the EA block without persisting i_file_acl=0, leaving a dangling on-disk pointer; after that block is reused, ext2_xattr_get() memcpy()s its contents to userspace when the header looks valid, so the filesystem-level UAF discloses other files' data.
- I:HIntegrity impact, high
- The lost i_file_acl update leaves the on-disk inode pointing at a freed EA block, so a later in-place xattr write can corrupt whatever reused that block, including other users' files and metadata; intended-durable IS_SYNC size/ctime/ACL updates can also fail to land, corrupting filesystem state.
- A:HAvailability impact, high
- Reloading the stale i_file_acl and reading an invalid reused EA block calls ext2_error(), which panics on errors=panic and remounts the volume read-only on errors=remount-ro; the resulting filesystem inconsistency can also render files and the volume unavailable.