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CVE-2026-89680
nfsd: fix nfsd_file leak on inter-server COPY setup failure
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem fs/nfsd. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89680 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When nfsd4_setup_inter_ssc() fails, nfsd4_copy() returns nfserr_offload_denied directly, bypassing the out: label where release_copy_files() would drop the nf_dst reference taken by nfs4_preprocess_stateid_op(). Each failed inter-server COPY leaks one nfsd_file, pinning file/inode/dentry/vfsmount. Fix by setting status and jumping to out: instead of returning directly.
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/nfs4proc.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, sid, bookworm · linux-6.12m
- 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
- 2026-09-11 (37 days 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
- 0.65%, higher than 50.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- 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 |
|---|---|---|
| 5.6 | 6.12.109 | 1a6a41b84845 |
| 5.6 | 6.18.50 | 424d5c95108a |
| 5.6 | 7.2.4 | 6ed8d6de7ec9 |
| 5.6 | 7.3 | 88a76145451d |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | 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:NAttack vector, network
- nfsd's NFSv4.2 OP_COPY is reached over TCP/2049: svc_recv to nfsd_dispatch to nfsd4_proc_compound to nfsd4_copy to nfsd4_setup_inter_ssc. A remote client triggers the leak with a COMPOUND; no local access to the server is required.
- AC:LAttack complexity, low
- Once inter-server COPY offload is enabled, the attacker controls every trigger: async COPY on the wire, a valid dest write stateid, and a source nl4_server that makes nfsd4_interssc_connect fail (bad uaddr/netid or failed mount). No race or attacker-uncontrollable layout is required.
- PR:NPrivileges required, none
- Under default AUTH_SYS, EXCHANGE_ID/CREATE_SESSION and OPEN verify no secret; a remote client permitted by the export asserts a UID and obtains write stateids. This matches PR:N on the same nfsd4_copy path (CVE-2024-53073, CVE-2024-50241).
- UI:NUser interaction, none
- The attacker's own NFSv4.2 COMPOUND traffic drives nfsd4_copy; no administrator or local user on the server must mount, open a file, or otherwise interact beyond nfsd already serving an export.
- S:UScope, unchanged
- The leaked nfsd_file reference pins file/inode/dentry/vfsmount inside the NFS server kernel's own security authority; there is no VM, IOMMU, or sandbox boundary crossing.
- C:NConfidentiality impact, none
- The defect only skips nfsd_file_put() on an extra filecache reference taken by nfs4_preprocess_stateid_op(); there is no out-of-bounds read, use-after-free, or other disclosure of kernel memory to the client.
- I:NIntegrity impact, none
- COPY setup fails before nfsd_copy_range, so no file data is modified; the leaked reference is not attacker-controlled reused memory and yields no write or control-flow primitive.
- A:HAvailability impact, high
- Each failed inter-server COPY permanently leaks one nfsd_file ref, pinning the dest file/inode/dentry/vfsmount. Repeating against many created-then-unlinked files unbounded-pins slab and inodes and blocks umount, enabling remote kernel memory exhaustion and NFS server DoS.