CVE-2026-80856

What the bug is

fuse_do_setattr() takes filemap_invalidate_lock() for a DAX truncate (fault_blocked = true) and releases it at the out:/error: labels. But when a writeback flush is also needed, a write_inode_now() failure returns directly and leaks the lock, so any later fault or truncate on the file stalls on the stale rwsem. For example, truncate(2) on a setuid file reaches fuse_do_setattr() with both ATTR_SIZE and ATTR_MODE set: truncate(2) └─ do_truncate() ├─ dentry_needs_remove_privs() # S_ISUID └─ notify_change() # KILL_SUID -> ATTR_MODE └─ fuse_setattr() # no killpriv: │ # ia_valid |= ATTR_MODE └─ fuse_do_setattr() ├─ filemap_invalidate_lock() # IS_DAX && is_truncate └─ write_inode_now() # is_wb && ATTR_MODE └─ if (err) # e.g. daemon -> -EIO return err # <- lock leaked Fix this by adding an unlock label that releases the lock before returning the error, and use it for the fuse_dax_break_layouts() failure path as well.

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/dir.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 fuse

Prints 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

2026-09-04 (44 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.17%, higher than 5.3% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

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
5.10	5.15.220	8f14906ce910
5.10	6.1.187	03cfeeb13542
5.10	6.6.156	92588d187ba4
5.10	6.12.108	ea9fea370b8d
5.10	6.18.49	1758730d9eaa
5.10	7.1.13	dd278d954c0e
5.10	7.2.3	e8457ebfd77a
5.10	7.3	9afeca0d569c

Debian advisories