CVE-2026-80896
Received Received - Intake

Race Condition in Linux Kernel mshv_irqfd_deassign

Publication date: 2026-09-04

Last updated on: 2026-09-04

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: mshv: Fix race in mshv_irqfd_deassign mshv_irqfd_deactivate() and the hlist traversal of pt_irqfds_list require pt->pt_irqfds_lock to be held, but mshv_irqfd_deassign() omits it. This races with the EPOLLHUP path in mshv_irqfd_wakeup(), which does take the lock before calling mshv_irqfd_deactivate(). Additionally, mshv_irqfd_deactivate() uses hlist_del() which poisons the node pointers rather than resetting them. Since mshv_irqfd_is_active() relies on hlist_unhashed() (checks pprev == NULL), a poisoned node still appears active. If a concurrent path calls mshv_irqfd_deactivate() again on the same irqfd, the guard fails to prevent a double hlist_del() on poisoned pointers. Fix both issues: - Add the missing spin_lock_irq/spin_unlock_irq around the list traversal in mshv_irqfd_deassign(), matching mshv_irqfd_release(). - Use hlist_del_init() instead of hlist_del() so the node is properly marked as unhashed after removal, making the is_active guard reliable.

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Meta Information

Published
2026-09-04
Last Modified
2026-09-04
Generated
2026-09-05
AI Q&A
2026-09-04
EPSS Evaluated
N/A
NVD
CVE-2026-80896
EUVD
EUVD-2026-71646

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a race condition in the Linux kernel's mshv (Microsoft Hypervisor) component. It occurs when mshv_irqfd_deassign() fails to hold a required lock while accessing shared data structures, allowing a concurrent operation to interfere. The issue involves improper handling of interrupt file descriptors (irqfd) where a double deletion of the same node can happen due to poisoned pointers not being reset.

Detection Guidance

This vulnerability is specific to the Linux kernel's mshv (Microsoft Hyper-V) subsystem and requires kernel-level inspection. Detection involves checking kernel logs for race conditions or double deletions in mshv_irqfd operations. Use commands like dmesg | grep mshv or journalctl -k | grep mshv to search for related errors. If you suspect exploitation, monitor for kernel panics or unexpected behavior in virtualized environments using Hyper-V.

Impact Analysis

This vulnerability could lead to system instability or crashes in virtualized environments using the Linux kernel's mshv. An attacker with local access might exploit the race condition to cause denial-of-service conditions or potentially execute arbitrary code in the host system.

Mitigation Strategies

Apply the latest kernel patches from your Linux distribution to resolve the race condition in mshv_irqfd_deassign. If patching is not immediately possible, disable the mshv module using modprobe -r mshv or blacklist it in /etc/modprobe.d/. Restrict access to Hyper-V virtual machines and monitor for unusual activity in virtualized environments.

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