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CVE-2026-98169

smb: client: fix potential OOB read in smb3_enum_snapshots()

7.1 EPSS 0.4% AV:N

Published 2026-10-06 (13 days ago) by the Linux kernel CNA. Subsystem fs/smb. Debian urgency: not yet assigned.

What to do, per Debian release

Debian's own status for CVE-2026-98169 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	fixedDLA-4841-1 · 2026-10-17 · text	6.1.190-1	Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts.
Debian 13trixie	fixedDSA-6568-1 · 2026-10-16 · text	6.12.113-1	Update the kernel and reboot. DSA-6568-1 shipped the fix on 2026-10-16, in 6.12.113-1. A running kernel keeps the old code until the machine restarts.
Debian 14forky	fixed	7.2.8-1	Update the kernel and reboot. Fixed in 7.2.8-1. A running kernel keeps the old code until the machine restarts.
Debian unstablesid	fixed	7.2.8-1	Update the kernel and reboot. Fixed in 7.2.8-1. A running kernel keeps the old code until the machine restarts.

The vulnerability

What the bug is

If snapshot_array_size is smaller than GMT_TOKEN_SIZE, smb3_enum_snapshots() sets ret_data_len to sizeof(struct smb_snapshot_array) without verifying the actual length of the server's reply. Because SMB2_ioctl() places no lower bound on the server-supplied OutputCount and allocates retbuf to exactly that length, a short reply results in ret_data_len exceeding the size of retbuf. The subsequent copy_to_user() then reads past the end of retbuf, leaking adjacent slab memory to userspace. The subsequent clamp check is ineffective as it only reduces ret_data_len. Fix this by rejecting replies shorter than sizeof(struct smb_snapshot_array) with -EIO. Note that the bound is set to the 12-byte struct size rather than the 16-byte MIN_SNAPSHOT_ARRAY_SIZE defined in MS-SMB2 3.3.5.15.1, because 12 bytes is exactly what copy_to_user() attempts to read.

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/smb/client/smb2ops.c

What this is: COMMON INTERNET FILE SYSTEM CLIENT (CIFS and SMB3)MAINTAINERS section matched on fs/smb/client/ · linux-cifs@vger.kernel.org · Supported
Kernel module: cifs

Check it on the machine

grep -wE 'CONFIG_CIFS|CONFIG_SMBFS' /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 cifs

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 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_CIFS, CONFIG_SMBFS
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

Debian tracker CVE record NVD kernel CNA record

Signals

Published: 2026-10-06 (13 days ago)source
CVSS: 7.1 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:Hsource recompute it
Attack vector: network (AV:N)source
EPSS: 0.43%, higher than 36.1% of all CVEssource
CISA KEV: not listedthe KEV catalogue
Debian urgency: not yet assignedsource
Subsystem: fs/smb

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
4.19	6.1.189	15a221c734b9
4.19	6.6.158	74995ee8305a
4.19	6.12.112	210f0f1f6781
4.19	6.18.54	1cdf0d304d82
4.19	7.2.8	dbe452a905df
4.19	7.3	4775c3b7a597
4.9.125	0	0
4.14.68	0	0
4.18.6	0	0

Debian advisories

Advisory	Date	Shipped to	Debian
DLA-4841-1	2026-10-17	bookworm 6.1.190-1	tracker
DSA-6568-1	2026-10-16	trixie 6.12.113-1	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: The bad input is the OutputCount field of the SMB2 IOCTL response to FSCTL_SRV_ENUMERATE_SNAPSHOTS, sent by the SMB server over TCP. SMB2_ioctl() rejects only 0 or oversized values and kmemdup()s 1-11 bytes, and smb3_enum_snapshots() then copies 12 bytes from that buffer.
AC:LAttack complexity, low: A server that always answers the snapshot FSCTL with OutputCount 1-11 hits the bug every time a caller passes snapshot_array_size < GMT_TOKEN_SIZE, which is the normal first sizing query. No race or memory layout outside the server's control is needed.
PR:NPrivileges required, none: The attacker is the SMB server answering the client's request. It needs no account or privilege on the client to send a short IOCTL response.
UI:RUser interaction, required: A victim has to mount the attacker's share, and a process on the client has to issue ioctl(CIFS_ENUMERATE_SNAPSHOTS) on a file there to make smb3_enum_snapshots() run.
S:UScope, unchanged: The out-of-bounds read and the crash both stay inside the client kernel. No VM, IOMMU or other security boundary is crossed.
C:LConfidentiality impact, low: copy_to_user() reads at most 11 bytes past the kmemdup'd retbuf, from the next kmalloc-8 object or the unused tail of a kmalloc-16 object. The leak is small and fixed in size, and it goes to the ioctl caller, not back over the wire.
I:NIntegrity impact, none: The defect is a read only: retbuf is copied out to user space, and no kernel memory is written out of bounds.
A:HAvailability impact, high: With CONFIG_HARDENED_USERCOPY (common on distro and Android kernels), a 12-byte copy_to_user() from a kmalloc-8 retbuf (OutputCount 1-8) fails the heap object check. usercopy_abort() then calls BUG() and the kernel oopses, or panics if panic_on_oops is set. The server can trigger this on every enumeration.