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CVE-2026-64160
netfs: Fix potential for tearing in ->remote_i_size and ->zero_point
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem fs/9p. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64160 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 | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Fix potential tearing in using ->remote_i_size and ->zero_point by copying i_size_read() and i_size_write() and using the same seqcount as for i_size. We need to make sure that netfslib and the filesystems that use it always hold i_lock whilst updating any of the sizes to prevent i_size_seqcount from getting corrupted.
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/9p/v9fs_vfs.h
fs/9p/vfs_inode.c
fs/9p/vfs_inode_dotl.c
fs/afs/file.c
fs/afs/inode.c
fs/afs/internal.h
fs/afs/write.c
fs/netfs/buffered_read.c
fs/netfs/buffered_write.c
fs/netfs/direct_write.c
fs/netfs/misc.c
fs/netfs/write_collect.c
- What this is
- 9P FILE SYSTEMMAINTAINERS section matched on fs/9p/ · v9fs@lists.linux.dev · Maintained
- Kernel module
- 9p
Check it on the machine
grep -w CONFIG_9P_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 9pPrints 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_9P_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
- 2026-07-19 (3 months 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
- 0.55%, higher than 45.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/9p
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.18 | 7.0.11 | 55970f238d49 |
| 5.18 | 7.1 | 2c8f4742bb76 |
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
- The bug is in netfs client code (CIFS/SMB, AFS, 9p) reached when processing network filesystem protocol responses and concurrent I/O; a malicious remote server can drive attribute/size updates that race with client read/write paths.
- AC:LAttack complexity, low
- The attacker controls both sides of the race by timing SMB/AFS/9p responses against concurrent local read/write/DIO operations, or by spawning parallel threads performing file I/O on the same inode.
- PR:NPrivileges required, none
- A remote malicious filesystem server needs no privileges on the victim host; exploitation only requires the victim system to perform routine I/O against a mounted attacker-controlled or MITM'd network share.
- UI:NUser interaction, none
- No per-attack discretionary user action is required beyond an existing CIFS/AFS/9p mount and normal automated or concurrent file access, which is typical in enterprise and embedded deployments.
- S:UScope, unchanged
- Impact is confined to the victim kernel's netfs client subsystem and does not cross a VM, IOMMU, or other security-authority boundary.
- C:HConfidentiality impact, high
- Torn 64-bit size values produce attacker-influenceable arbitrary bounds used in read-length and EOF decisions, potentially causing out-of-bounds kernel reads or stale-cache data exposure beyond intended file ranges.
- I:HIntegrity impact, high
- Corrupted size metadata causes incorrect zero-filling, skipped server reads, and wrong EOF handling, enabling arbitrary modification of file content visible to applications and incorrect size metadata written back to the server.
- A:HAvailability impact, high
- Unsynchronized writes can corrupt i_size_seqcount, causing i_size_read() and related readers to spin forever, producing soft lockups and denial of service for affected inodes and dependent processes.