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CVE-2026-64265
fuse: clear intr_entry in fuse_resend and fuse_remove_pending_req
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-2026-64265 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 | 6.12.96-1 | Update the kernel and reboot. Fixed in 6.12.96-1. A running kernel keeps the old code until the machine restarts. |
| 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. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4724-1 · 2026-08-07 · text | 6.12.100-1~deb12u1 | Update the kernel and reboot. DLA-4724-1 shipped the fix on 2026-08-07, in 6.12.100-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When fuse_resend() moves a request from fpq->processing back to fiq->pending, it sets FR_PENDING and clears FR_SENT but does not remove the requests intr_entry from fiq->interrupts. If the request had FR_INTERRUPTED set from a prior signal, intr_entry remains dangling on fiq->interrupts. When the requesting task then receives a fatal signal, fuse_remove_pending_req() sees FR_PENDING=1, removes the request from fiq->pending and frees it via the refcount path, also without cleaning intr_entry. The stale intr_entry causes use-after-free when fuse_read_interrupt() iterates fiq->interrupts: - list_del_init(&req->intr_entry) -> UAF write on freed slab - req->in.h.unique -> UAF read, data leaked to userspace Remove intr_entry from fiq->interrupts in fuse_resend() for interrupted requests before they are placed back on fiq->pending. Add a WARN_ON if the intr_entry is not empty on request destruction.
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.c
- What this is
- FUSE FILESYSTEM [CORE]MAINTAINERS section matched on fs/fuse/ · fuse-devel@lists.linux.dev · Supported
- Kernel module
- fuse
Check it on the machine
grep -w CONFIG_FUSE_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 fusePrints 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 code. Every release below compiles the affected file into the kernels it ships.
- bookwormm
- trixie, forky, sid, bookworm · linux-6.12y
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_FUSE_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
- 2026-07-25 (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
- 0.17%, higher than 6.1% 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 |
|---|---|---|
| 6.9 | 6.12.96 | 1d8ecd0cd696 |
| 6.9 | 6.18.39 | 7366e6f4d2b4 |
| 6.9 | 7.1.4 | 893479015cb6 |
| 6.9 | 7.2 | f8fce75fedf7 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4724-1 | 2026-08-07 | bookworm 6.12.100-1~deb12u1 | tracker |
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 through local filesystem, signal, and read/write syscalls involving an attached /dev/fuse descriptor. No network or physical input directly reaches the vulnerable functions.
- AC:LAttack complexity, low
- A malicious FUSE daemon can deterministically withhold a request, signal its client, issue FUSE_NOTIFY_RESEND, deliver a fatal signal, and read the stale interrupt. Polling permits synchronization without depending on an uncontrollable race.
- PR:LPrivileges required, low
- Normal FUSE supports user-namespace and non-privileged mounts, while opening the FUSE device has no kernel capability check. An ordinary user can control both the daemon and client processes in a reasonable deployment.
- UI:NUser interaction, none
- All triggering operations can be performed programmatically by attacker-controlled daemon and client processes. No separate victim must mount or access the filesystem.
- S:UScope, unchanged
- Exploitation compromises the same kernel security authority in which the vulnerable FUSE code executes. This is a standard local kernel privilege escalation rather than a guest-to-host boundary escape.
- C:HConfidentiality impact, high
- fuse_read_interrupt() reads req->in.h.unique from freed slab memory and copies it to userspace. Slab reuse or cache merging can expose replacement-object contents through this UAF read.
- I:HIntegrity impact, high
- list_del_init() interprets freed or reused intr_entry pointers as live list links and writes through them as well as into the freed object. Heap grooming can leverage this memory corruption for arbitrary writes or control-flow compromise.
- A:HAvailability impact, high
- The stale list pointers and UAF writes can corrupt kernel queues or slab objects and cause an oops or panic. The attacker can repeat the deterministic trigger sequence.