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CVE-2026-64066
netfs: Fix netfs_read_to_pagecache() to pause on subreq failure
Published 2026-07-19 (3 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-2026-64066 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 | 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 netfs_read_to_pagecache() so that it pauses the generation of new subrequests if an already-issued subrequest fails.
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/buffered_read.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 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.
- bookworm, trixie, forky, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- 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
- 2026-07-19 (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
- 0.65%, higher than 50.1% 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 |
|---|---|---|
| 6.12 | 6.18.34 | 884c4c4f35e5 |
| 6.12 | 7.0.11 | 0256e79ce421 |
| 6.12 | 7.1 | 8a8c0cfdf465 |
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 hit when processing failed network filesystem read completions from remote SMB/NFS/Ceph/9p servers; a malicious or compromised server can trigger mid-read I/O errors over the network during buffered readahead without local kernel access.
- AC:LAttack complexity, low
- An attacker controlling the remote server can reliably cause read failures during large multi-subrequest readahead, and controls the timing of async completions that race the issuer thread; no uncontrollable conditions are required.
- PR:NPrivileges required, none
- The attacker operates as a remote malicious network filesystem server and needs no local privileges on the victim; any user with read access to an already-mounted share can trigger the vulnerable path via normal file reads.
- UI:NUser interaction, none
- Exploitation requires only routine file access on pre-mounted enterprise NAS/CIFS home directories or auto-mounted virtio-fs/9p shares, with no additional victim action beyond normal reads.
- S:UScope, unchanged
- Impact is kernel memory corruption and potential local privilege escalation within the same kernel security boundary, not a VM escape or cross-authority boundary bypass.
- C:HConfidentiality impact, high
- Concurrent issuer/collector manipulation of rolling_buffer folio_queues after subrequest failure can cause use-after-free and out-of-bounds access on kernel heap objects, enabling arbitrary memory disclosure.
- I:HIntegrity impact, high
- The race allows continued I/O and buffer advancement after failure handling has abandoned regions, corrupting pagecache folio state and heap metadata in ways that can be leveraged for arbitrary kernel writes or code execution.
- A:HAvailability impact, high
- The synchronization bug causes kernel memory corruption that can trigger oops, BUG, or panic; even without full exploitation, repeated triggering causes system crashes.