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CVE-2026-89921: KVM: s390: Zero initialize data structures for inject_pfault_token

• Severity: unknown
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-16 · updated 2026-10-30

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.

Affected products

• Linux: 3.19 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux 7.3. Check the vendor advisory for mitigations.

References

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

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