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CVE-2026-52967
smb/client: fix possible infinite loop and oob read in symlink_data()
Published 2026-06-24 (4 months 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-2026-52967 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-4665-1 · 2026-07-03 · text | 6.1.176-1 | Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
On 32-bit architectures, the infinite loop is as follows: len = p->ErrorDataLength == 0xfffffff8 u8 *next = p->ErrorContextData + len next == p On 32-bit architectures, the out-of-bounds read is as follows: len = p->ErrorDataLength == 0xfffffff0 u8 *next = p->ErrorContextData + len next == (u8 *)p - 8
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/smb2file.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, 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
Signals
- Published
- 2026-06-24 (4 months ago)source
- CVSS
- 8.1 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.39%, higher than 31.9% 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 |
|---|---|---|
| 6.1 | 6.1.175 | 1cfa2d59f669 |
| 6.1 | 6.6.141 | b41598bf54b3 |
| 6.1 | 6.12.91 | cd4b9b662f0f |
| 6.1 | 6.18.33 | 97a05b0ae9ea |
| 6.1 | 7.0.10 | 1b9331b16b0e |
| 6.1 | 7.1 | 7d9a7f1f96cd |
| 6.0.16 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4671-1 | 2026-07-05 | bullseye 6.1.176-1~deb11u1 | tracker |
| DLA-4665-1 | 2026-07-03 | bookworm 6.1.176-1 | 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 vulnerable SMB client parser consumes an SMB2 CREATE error response supplied by a remote SMB server over the network. A malicious or compromised SMB share can send the crafted `STATUS_STOPPED_ON_SYMLINK` response.
- AC:LAttack complexity, low
- The server directly controls `ErrorContextCount`, `ByteCount`, `ErrorId`, and `ErrorDataLength`, and no race or hard-to-hit state is required. Although the wraparound behavior is 32-bit specific, that is a deployment property rather than an attacker-uncontrolled exploitation condition.
- PR:NPrivileges required, none
- The attacker needs no privileges on the victim system; they only need to operate or control the SMB server endpoint that the client connects to. The path can also be reached through guest or null-auth SMB sessions.
- UI:RUser interaction, required
- The victim client must mount/connect to the SMB share and perform a path operation such as lookup, stat, open, or create that causes an SMB2 CREATE response to be parsed. The remote server cannot trigger this parser without client-side filesystem activity.
- S:UScope, unchanged
- The affected component is the Linux kernel SMB client, and the impact is to the same kernel/client security authority. This is not a VM escape, IOMMU bypass, or cross-scope sandbox escape.
- C:HConfidentiality impact, high
- The bug is an out-of-bounds kernel read in a server-controlled response parser, and the read is not strictly bounded to only a few harmless bytes. Following the required conservative rule, this is scored as high confidentiality impact.
- I:NIntegrity impact, none
- The defect advances a parser pointer incorrectly and reads from the wrong location, but it does not write out of bounds or provide a kernel memory write primitive. No direct integrity impact beyond normal malicious-server control of SMB content was identified.
- A:HAvailability impact, high
- The crafted length can make the parser loop indefinitely on 32-bit systems, causing a reliable denial of service. Other malformed pointer positions can also lead to invalid kernel reads and possible oops conditions.