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CVE-2026-64261
fuse-uring: Avoid use-after-free in fuse_uring_async_stop_queues
Published 2026-07-25 (3 months ago) by the Linux kernel CNA. Subsystem fs/fuse. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64261 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 | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
fuse_uring_async_stop_queues() might run when the last reference on ring->queue_refs was already dropped. In order to avoid an early destruction a reference on struct fuse_conn is now taken before starting fuse_uring_async_stop_queues() and that reference is only released when that delayed work queue terminates.
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/fuse/dev_uring.c
- What this is
- FUSE FILESYSTEM [IO-URING]MAINTAINERS section matched on fs/fuse/dev_uring.c · fuse-devel@lists.linux.dev · Maintained
Check it on the machine
grep -wE 'CONFIG_FUSE_FS|CONFIG_FUSE_IO_URING' /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 builds this code. Every release with an answer below compiles the affected file into the kernels it ships. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidy
- ?
- not established - no Makefile entry for the affected file
- y
- built into the kernel image on every flavour - only a patch removes it
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 switches
- CONFIG_FUSE_FS, CONFIG_FUSE_IO_URING
- Reads as
- all on means the file is compiled; any one off means it is not.
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
- 2026-07-25 (3 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.16%, higher than 4.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- fs/fuse
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.14 | 6.18.39 | 23a356e0bd96 |
| 6.14 | 7.1.4 | 95d7f50aff2a |
| 6.14 | 7.2 | d351da750669 |
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 vulnerability is reached locally through IORING_OP_URING_CMD on a FUSE or CUSE device and connection teardown; no network path invokes it.
- AC:LAttack complexity, low
- The attacker controls ring-entry creation or cancellation and closing the final channel, allowing both sides of the race to be driven and retried.
- PR:LPrivileges required, low
- The vulnerable io_uring handler has no capability check, and a basic user can access a delegated FUSE/CUSE device; FUSE also supports unprivileged user-namespace mounts.
- UI:NUser interaction, none
- The attacker can create the connection, issue concurrent io_uring operations, and initiate teardown without any separate victim action.
- S:UScope, unchanged
- Exploitation compromises the same host kernel security authority; this is standard local kernel privilege escalation rather than a VM or IOMMU boundary escape.
- C:HConfidentiality impact, high
- The stale delayed worker accesses reclaimed kmalloc-192 ring, queue, and list objects, allowing heap replacement to turn the UAF into kernel-memory disclosure primitives.
- I:HIntegrity impact, high
- The worker performs list and synchronization operations through freed, reclaimable pointers, making arbitrary writes or control-flow hijacking and kernel code execution defensible.
- A:HAvailability impact, high
- The bug has produced a KASAN slab-use-after-free in asynchronous queue teardown and can cause a kernel oops, panic, or unrecoverable list corruption.