CVE-2026-98900: xen/gntalloc: validate grant count before allocation

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: 2026-10-23 · updated 2026-10-26

Description

In the Linux kernel, the following vulnerability has been resolved: xen/gntalloc: validate grant count before allocation gntalloc_ioctl_alloc() allocates the grant-id array before checking whether the requested count fits within the global grant limit. Counts above that limit cannot succeed, so reject them before the user-controlled allocation reaches kcalloc(). Use a subtraction-based check while holding gref_mutex so adding the requested count cannot wrap. Also cast the count before advancing the per-file index so the page-size multiplication is performed in 64-bit arithmetic.

Affected products

Linux kernel: before 5.10.271; before 5.15.222; before 6.1.189; before 6.6.158; before 6.12.111; before 6.18.53 — fixed in 5.10.271, 5.15.222, 6.1.189, 6.12.111, 6.18.53, 6.6.158

How to fix

Upgrade to a fixed version: Linux kernel 5.10.271, 5.15.222, 6.1.189, 6.12.111. Check the vendor advisory for mitigations.

References

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