Look up another CVE · open CVE-2026-89443 in the interactive tracker
CVE-2026-89443
platform/x86: ISST: Validate level in perf mask ioctls
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem drivers/platform. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-89443 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
isst_if_get_perf_level_mask() and isst_if_get_base_freq_mask() use the user-provided level as an index into perf_levels[] via _read_pp_level_info() and _read_bf_level_info(), but neither helper validates it first. The adjacent level-info helpers reject levels above max_level before reading the same per-level register block. Add the same bounds checks to the mask helpers, and reject disabled SST-PP levels in isst_if_get_perf_level_mask() to match isst_if_get_perf_level_info(). This prevents out-of-bounds reads from the per-level offset table on invalid ioctl input.
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.
drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
- What this is
- INTEL SPEED SELECT TECHNOLOGYMAINTAINERS section matched on drivers/platform/x86/intel/speed_select_if/ · platform-driver-x86@vger.kernel.org · Maintained
- Kernel module
- isst_tpmi_core
Check it on the machine
grep -wE 'CONFIG_INTEL_SPEED_SELECT_INTERFACE|CONFIG_INTEL_SPEED_SELECT_TPMI|CONFIG_X86' /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 isst_tpmi_corePrints 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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed. The build rule could not be established for 1 release, so nothing is claimed about those.
- bookworm?
- trixieMnot built on amd64/cloud-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidMnot built on amd64/cloud-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k
- ?
- not established - no Makefile entry for the affected file
- M
- a module where it is built at all; some flavours do not build it
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switches
- CONFIG_INTEL_SPEED_SELECT_INTERFACE, CONFIG_INTEL_SPEED_SELECT_TPMI, CONFIG_X86
- 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
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.16%, higher than 5.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/platform
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.4 | 6.6.157 | beb22ebf76c0 |
| 6.4 | 6.12.109 | 1a8bab5ceee1 |
| 6.4 | 6.18.50 | 1889a9156553 |
| 6.4 | 7.2.4 | d19385624bdf |
| 6.4 | 7.3 | 80e0d353c86a |
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
- The bug is reached only via local ioctl(ISST_IF_GET_PERF_LEVEL_CPU_MASK or ISST_IF_GET_BASE_FREQ_CPU_MASK) on /dev/isst_interface, dispatched through isst_if_def_ioctl() to the TPMI SST helpers; there is no network, Bluetooth, or physical-device path into these functions.
- AC:LAttack complexity, low
- The attacker fully controls the ioctl argument, including the 8-bit level used as perf_levels[level] with no pre-fix bounds check; the out-of-bounds table read and following MMIO readq() occur deterministically, with no race or attacker-uncontrollable memory layout required.
- PR:LPrivileges required, low
- isst_if_open() and both GET mask ioctls perform no capable() check; CAP_SYS_ADMIN is required only for SST write/set commands, so a local process that can open /dev/isst_interface can reach this read path without init-namespace admin capabilities.
- UI:NUser interaction, none
- The attacker opens /dev/isst_interface and issues the crafted ioctl from their own process; no separate victim action such as mounting a filesystem or opening a file is required.
- S:UScope, unchanged
- The out-of-bounds kernel/MMIO read and any resulting oops stay within the host kernel security authority; this is not a VM escape, IOMMU bypass, or other cross-boundary impact.
- C:HConfidentiality impact, high
- User-supplied level (0-255) indexes perf_levels[] (at most 8 entries), reading adjacent heap as a signed mmio_offset that is then used in readq(); the 64-bit result is copied to userspace when punit_cpu_map is set, an out-of-bounds read rated High unless strictly a few bytes.
- I:NIntegrity impact, none
- Both helpers only issue MMIO readq() and copy_to_user of the resulting mask; there is no writeq, heap write, type confusion, or control-flow hijack primitive on this path.
- A:HAvailability impact, high
- sst_base is a bounded ioremap from devm_ioremap_resource(); a heap-derived mmio_offset can drive readq() outside that mapping and oops, and the perf_levels[] over-read itself can fault on hardened kernels; any kernel crash is High availability impact.