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CVE-2026-74316
NFSD: Handle layout stid in nfsd4_drop_revoked_stid()
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem fs/nfsd. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-74316 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 | 6.12.100-1 | 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
nfsd4_drop_revoked_stid() has no SC_TYPE_LAYOUT case, so when a client sends FREE_STATEID for an admin-revoked layout stid, the default branch releases cl_lock and returns without unhashing or releasing the stid. The stid remains in the IDR and on the per-client list until the client is destroyed. Remove the layout stid from the per-client list and call nfs4_put_stid() to drop the creation reference. When the refcount reaches zero, nfsd4_free_layout_stateid() handles the remaining cleanup: cancelling the fence worker, removing from the per-file list, and freeing the slab object.
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/nfsd/nfs4state.c
- What this is
- KERNEL NFSD, SUNRPC, AND LOCKD SERVERSMAINTAINERS section matched on fs/nfsd/ · linux-nfs@vger.kernel.org · Supported
- Kernel module
- nfsd
Check it on the machine
grep -wE 'CONFIG_NFSD|CONFIG_NFSD_V4' /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 nfsdPrints 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 switches
- CONFIG_NFSD, CONFIG_NFSD_V4
- 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
- 2026-08-15 (2 months ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.63%, higher than 49.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- fs/nfsd
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.9 | 6.12.97 | 7ed62f7040ee |
| 6.9 | 6.18.40 | da6f86ff4f2d |
| 6.9 | 7.1.5 | 8024028ef916 |
| 6.9 | 7.2 | 86b9898920a6 |
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 flaw is reached through nfsd's NFSv4 OP_FREE_STATEID handler, processing attacker-controlled RPC compounds over the network on TCP port 2049 via nfsd_dispatch to nfsd4_proc_compound to nfsd4_free_stateid.
- AC:LAttack complexity, low
- Once a client holds admin-revoked pNFS layout stateids, sending FREE_STATEID reliably triggers the leak every time; the attacker controls layout acquisition and the freeing RPC on both sides of the interaction.
- PR:NPrivileges required, none
- Exploitation requires only remote NFSv4 client access to a pNFS-enabled export (EXCHANGE_ID/CREATE_SESSION plus FREE_STATEID), not local shell access or elevated privileges on the Linux host.
- UI:NUser interaction, none
- No administrator or end-user action on the server is required beyond normal NFS service exposure; the leak is triggered entirely by malicious NFS protocol traffic from a network client.
- S:UScope, unchanged
- Impact is confined to kernel memory and nfsd state management within the same kernel security boundary; there is no VM escape, container breakout, or cross-authority boundary crossing.
- C:NConfidentiality impact, none
- The bug retains unreleased layout stateid structures in the IDR and per-client lists without corrupting memory or exposing kernel data; there is no out-of-bounds read or information disclosure primitive.
- I:NIntegrity impact, none
- No data modification or memory corruption occurs; the stateid is simply not freed when it should be, leaving stale entries without enabling arbitrary writes or code execution.
- A:HAvailability impact, high
- Each triggered FREE_STATEID permanently leaks a layout stateid slab object and IDR slot until client teardown; a remote NFS client can repeat this for every admin-revoked pNFS layout, causing unbounded kernel memory consumption and nfsd DoS.