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CVE-2026-72364
netfs: Fix writeback error handling
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem fs/netfs. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72364 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Fix the error handling in writeback_iter() loop. If an error occurs, writeback_iter() needs to be called again with *error set to the error so that it can clean up iteration state. Further, the current folio needs unlocking and redirtying.
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/netfs/write_issue.c
- What this is
- FILESYSTEMS [NETFS LIBRARY]MAINTAINERS section matched on fs/netfs/ · netfs@lists.linux.dev · Supported
- Kernel module
- netfs
Check it on the machine
grep -w CONFIG_NETFS_SUPPORT /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 netfsPrints 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 as a loadable module. Every release with an answer below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded. The build rule could not be established for 1 release, so nothing is claimed about those.
- bookworm?
- trixie, forky, sidm
- ?
- not established - no Makefile entry for the affected file
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switch
- CONFIG_NETFS_SUPPORT
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
- 2026-08-15 (2 months ago)source
- CVSS
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 6.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- fs/netfs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.10 | 6.12.97 | fb39ffd3cc54 |
| 6.10 | 6.18.40 | 1bb33d959aab |
| 6.10 | 7.1.5 | 89df9c158a25 |
| 6.10 | 7.2 | ac5f95ac5d6d |
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 bug is in client-side netfs writeback reached only via local VFS writeback (do_writepages -> netfs_writepages) on CIFS, 9p, and AFS mounts after local writes/mmaps dirty pagecache; it is not in ksmbd/nfsd or other packet-receive paths.
- AC:LAttack complexity, low
- An attacker can reliably trigger -ENOMEM during writeback by exhausting the 100-entry folio_queue mempool or system memory while dirtying many pages on a netfs mount, then forcing writeback via sync/fsync, close, or reclaim.
- PR:LPrivileges required, low
- Exploitation requires a local process with write access to files on a netfs-backed mount (typical unprivileged CIFS/9p/AFS user); no real-root or init-namespace-only capability is needed beyond normal filesystem permissions.
- UI:NUser interaction, none
- No victim interaction is required beyond normal background writeback or attacker-initiated sync/memory pressure; exploitation does not depend on a victim opening a file or mounting a share at attack time.
- S:UScope, unchanged
- Impact is confined to the kernel pagecache and netfs writeback state on the affected host; it does not cross VM, container, or IOMMU security boundaries into another authority.
- C:NConfidentiality impact, none
- The flaw mishandles folio locks and dirty state causing data loss or hangs; it does not expose kernel memory, leak pointers, or provide an out-of-bounds or use-after-free read primitive.
- I:HIntegrity impact, high
- On -ENOMEM at writeback start the vulnerable path calls netfs_kill_dirty_pages(), which clears dirty folios without uploading them, silently destroying arbitrary unsaved buffered data on network filesystem mounts.
- A:HAvailability impact, high
- Breaking out of the writeback_iter loop on error leaves folios locked and writeback state uncleared, causing indefinite blocking of processes accessing those pages and stalling future writeback on affected files.