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CVE-2026-93801
smb/client: zero-initialize stack-allocated cifs_open_info_data
Published 2026-09-24 (24 days ago) by the Linux kernel CNA. Subsystem fs/smb. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-93801 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 | 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
Stack-allocated cifs_open_info_data may contain random data. This can make some fields have wrong value if they are not set later.
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/link.c
fs/smb/client/smb1ops.c
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 cifsPrints 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_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
Signals
- Published
- 2026-09-24 (24 days ago)source
- CVSS
- 7.0 high
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.12%, higher than 1.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- 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 |
|---|---|---|
| 6.12.54 | 6.12.111 | 74ff47e6c421 |
| 6.18 | 6.18.53 | 22532dd88694 |
| 6.18 | 7.2 | 8fce4cf4369c |
| 6.6.113 | 0 | 0 |
| 6.17.4 | 0 | 0 |
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:LAttack vector, local
- smb_set_file_info, cifs_query_mf_symlink, and __cifs_sfu_make_node allocate cifs_open_info_data on the stack and pass it to open/query_path_info. Those run only from local VFS setattr (cifs_setattr_nounix), O_TMPFILE (set_tmpfile_attr), sfu mknod/symlink, and MF-symlink lookup (check_mf_symlink), not from ksmbd or demux-thread PDU parsing.
- AC:HAttack complexity, high
- smb_set_file_info calls cifs_query_path_info, which walks uninitialized wsl.eas, only when the SMB1 session lacks CAP_NT_SMBS, and that walk runs only after the query sets reparse_point from ATTR_REPARSE_POINT. A local attacker cannot strip CAP_NT_SMBS or force that DOS attribute on a typical NT/SMB2/SMB3 server.
- PR:LPrivileges required, low
- cifs_setattr_nounix → cifs_set_file_info needs only inode ownership or directory write (utimensat, chmod clearing ATTR_READONLY, O_TMPFILE via set_tmpfile_attr). CIFS is not FS_USERNS_MOUNT, but using an already-mounted share does not require init-namespace CAP_SYS_ADMIN.
- UI:NUser interaction, none
- The attacker issues setattr, mknod/symlink, or lookup themselves on a share that is already mounted (fstab/autofs/CIFS home). No separate victim mount or open is required at exploit time.
- S:UScope, unchanged
- The stack out-of-bounds walk/write in cifs_query_path_info stays inside the client kernel CIFS code and does not cross a VM, IOMMU, or sandbox boundary.
- C:HConfidentiality impact, high
- With ATTR_REPARSE_POINT set, cifs_query_path_info walks data->wsl.eas using leftover next_entry_offset with no bound against SMB2_WSL_MAX_QUERY_EA_RESP_SIZE, an unbounded out-of-bounds read of kernel stack and adjacent memory.
- I:HIntegrity impact, high
- After that walk, CIFSSMBQAllEAs writes $LXMOD/$LXDEV through the wild ea pointer and the code stores next_entry_offset/ea_name_length/ea_value_length at that location, a stack out-of-bounds write.
- A:HAvailability impact, high
- The while (next) loop over uninitialized next_entry_offset can spin without bound or dereference unmapped memory and oops, hanging or crashing the setattr path.