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CVE-2026-64598
smb/client: Fix error code in smb2_aead_req_alloc()
Published 2026-08-06 (2 months ago) by the Linux kernel CNA. Subsystem fs/smb. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64598 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 | 6.12.96-1 | Update the kernel and reboot. Fixed in 6.12.96-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4724-1 · 2026-08-07 · text | 6.12.100-1~deb12u1 | Update the kernel and reboot. DLA-4724-1 shipped the fix on 2026-08-07, in 6.12.100-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The "*num_sgs" variable is a u32 so "ERR_PTR(*num_sgs)" doesn't work. We would have to do something similar to the previous line where it's cast to int and then long. However, it's simpler to store the return in an int ret variable. This bug would eventually result in a crash when dereference the invalid error pointer.
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 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
- 2026-08-06 (2 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.28%, higher than 18.9% 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 |
|---|---|---|
| 6.3 | 6.6.145 | aa37f5fef78d |
| 6.3 | 6.12.96 | cad756733dc3 |
| 6.3 | 6.18.39 | a187883cc1dc |
| 6.3 | 7.1.4 | a1cc432cb0b0 |
| 6.3 | 7.2 | 61f28012e565 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4724-1 | 2026-08-07 | bookworm 6.12.100-1~deb12u1 | 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 buggy smb2_aead_req_alloc()/crypt_message() path runs in the in-kernel SMB3 client during encrypted transform processing over an SMB network session; the highest-severity scenario is a client mounting and using an untrusted or malicious SMB3 encrypted share.
- AC:LAttack complexity, low
- When cifs_get_num_sgs() returns a negative errno, the u32 truncation makes ERR_PTR() bypass IS_ERR() deterministically on 64-bit, and the subsequent sg_init_marker()/pointer use crashes without requiring an attacker-uncontrollable race or memory layout.
- PR:NPrivileges required, none
- The attacking SMB endpoint or network adversary needs no privileges or account on the victim client; client-side credentials used to mount the share are a victim condition, not attacker privileges.
- UI:RUser interaction, required
- A victim must mount or otherwise use an SMB3 share with encryption so the client encrypt/decrypt AEAD allocation path runs; per CVSS guidance, mounting a filesystem is user interaction.
- S:UScope, unchanged
- The invalid error-pointer dereference and resulting kernel memory access remain within the client kernel's security authority and do not cross a VM, IOMMU, or sandbox boundary.
- C:HConfidentiality impact, high
- IS_ERR() failure leads to wild pointer use (uninitialized AEAD/sg state and invalid creq), which under the required uncertainty rule is treated as a high-impact kernel memory disclosure primitive rather than a pure non-leaking crash.
- I:HIntegrity impact, high
- The same path performs a wild write via sg_mark_end() on a bogus scatterlist address and may later kfree_sensitive() an invalid pointer, yielding kernel memory corruption; under uncertainty this is scored as high integrity impact.
- A:HAvailability impact, high
- The commit-documented result is a kernel crash from dereferencing the invalid error pointer; sg_init_marker() on a NULL sgl with a huge truncated nents count causes a reliable oops/panic DoS.