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CVE-2026-74359
configfs_lookup(): don't leave ->s_dentry dangling on failure
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem fs/configfs. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74359 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 | fixed | 6.1.180-1 | Update the kernel and reboot. Fixed in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| 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
Normally ->s_dentry is cleared when dentry it's pointing to becomes negative (on eviction, realistically). However, that only happens if dentry gets to be positive in the first place; in case of inode allocation failure dentry never becomes positive, so ->d_iput() is not called at all. We do part of what normally would've been done by configfs_d_iput() (dropping the reference to configfs_dirent) manually, but we do not clear ->s_dentry there. Sloppy as it is, it does not matter in case of configfs_create_{dir,link}() - there configfs_dirent does not survive dropping the sole reference to it. However, for configfs_lookup() it *does* survive, with a dangling pointer to soon to be freed dentry sitting it its ->s_dentry. Subsequent getdents(2) in that directory will end up dereferencing that pointer in order to pick the inode number. Use after free... This is the minimal fix; the right approach is to set the linkage between dentry and configfs_dirent only after we know that we have an inode, but that takes more surgery and the bug had been there since 2006, so...
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/configfs/dir.c
- What this is
- CONFIGFSMAINTAINERS section matched on fs/configfs/ · Supported
- Kernel module
- configfs
Check it on the machine
grep -w CONFIG_CONFIGFS_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 configfsPrints 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_CONFIGFS_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
- 2026-08-15 (2 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
- 0.13%, higher than 2.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/configfs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.16 | 5.15.212 | 3e83b2203aa5 |
| 2.6.16 | 6.1.178 | b6e9c82522dd |
| 2.6.16 | 6.6.145 | eee07d769da5 |
| 2.6.16 | 6.12.97 | 9c747dcee164 |
| 2.6.16 | 6.18.40 | c3b073a209a9 |
| 2.6.16 | 7.1.5 | 57088b06109f |
| 2.6.16 | 7.2 | 10da12d352b7 |
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 reached only via local VFS syscalls (openat/stat on a configfs attribute and getdents on its parent) against /sys/kernel/config; configfs is not exposed through network-facing kernel services such as ksmbd, nfsd, or the TCP/IP stack.
- AC:LAttack complexity, low
- Exploitation is a deterministic error-path bug, not a race: inode allocation failure in configfs_lookup() leaves sd->s_dentry dangling and a follow-up getdents reliably dereferences it; the attacker can force ENOMEM by applying memory pressure they control.
- PR:LPrivileges required, low
- Default configfs modes (0755 directories, 0644 attributes) let any local user read/list kernel-registered subsystem trees (e.g. nvmet, usb_gadget) without init-namespace root; mkdir/write still need admin, but triggering lookup on existing unpinned attributes does not.
- UI:NUser interaction, none
- No victim interaction is required beyond the attacker issuing their own syscalls on configfs paths; configfs is mounted at boot under /sys/kernel/config and exploitation does not depend on another user mounting or opening files.
- S:UScope, unchanged
- The use-after-free corrupts kernel heap memory and enables local privilege escalation within the same kernel security domain; it does not cross VM, IOMMU, or sandbox boundaries.
- C:HConfidentiality impact, high
- configfs_readdir() reads d_inode() through a dangling sd->s_dentry after failed lookup, giving a slab use-after-free read primitive on freed dentry/inode memory that can disclose kernel data or pointers via heap reuse.
- I:HIntegrity impact, high
- Reclaimed dentry/inode slabs let an attacker shape freed-object contents and convert the dangling pointer into arbitrary kernel writes and control-flow hijack, consistent with standard UAF exploitation of VFS objects.
- A:HAvailability impact, high
- Dereferencing the freed dentry during getdents causes kernel oops/panic (as described in the fix); the UAF is repeatable and can deny service even when full exploitation is not attempted.