Unity Linux 20.1050e Security Update: kernel (UTSA-2026-102139)

high Nessus Plugin ID 337324

Synopsis

The Unity Linux host is missing one or more security updates.

Description

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-102139 advisory.

In the Linux kernel, the following vulnerability has been resolved:

uio_hv_generic: Let userspace take care of interrupt mask

Remove the logic to set interrupt mask by default in uio_hv_generic driver as the interrupt mask value is supposed to be controlled completely by the user space. If the mask bit gets changed by the driver, concurrently with user mode operating on the ring, the mask bit may be set when it is supposed to be clear, and the user-mode driver will miss an interrupt which will cause a hang.

For eg- when the driver sets inbound ring buffer interrupt mask to 1, the host does not interrupt the guest on the UIO VMBus channel.
However, setting the mask does not prevent the host from putting a message in the inbound ring buffer.So lets assume that happens, the host puts a message into the ring buffer but does not interrupt.

Subsequently, the user space code in the guest sets the inbound ring buffer interrupt mask to 0, saying Hey, Im ready for interrupts.
User space code then calls pread() to wait for an interrupt.
Then one of two things happens:

* The host never sends another message. So the pread() waits forever.
* The host does send another message. But because theres already a message in the ring buffer, it doesnt generate an interrupt.
This is the correct behavior, because the host should only send an interrupt when the inbound ring buffer transitions from empty to not-empty. Adding an additional message to a ring buffer that is not empty is not supposed to generate an interrupt on the guest.
Since the guest is waiting in pread() and not removing messages from the ring buffer, the pread() waits forever.

This could be easily reproduced in hv_fcopy_uio_daemon if we delay setting interrupt mask to 0.

Similarly if hv_uio_channel_cb() sets the interrupt_mask to 1, theres a race condition. Once user space empties the inbound ring buffer, but before user space sets interrupt_mask to 0, the host could put another message in the ring buffer but it wouldnt interrupt.
Then the next pread() would hang.

Fix these by removing all instances where interrupt_mask is changed, while keeping the one in set_event() unchanged to enable userspace control the interrupt mask by writing 0/1 to /dev/uioX.

Tenable has extracted the preceding description block directly from the Unity Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Update the affected kernel package.

Plugin Details

Severity: High

ID: 337324

File Name: unity_linux_UTSA-2026-102139.nasl

Version: 1.1

Type: Local

Family: Unity Linux Local Security Checks

Published: 8/18/2026

Updated: 8/18/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 5.7

Percentile: 96.81

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 5.8

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C

CVSS Score Source: CVE-2025-40048

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Required KB Items: Host/local_checks_enabled, Host/cpu, Host/UOS-Server/release, Host/UOS-Server/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 8/17/2026

Vulnerability Publication Date: 10/23/2025

Reference Information

CVE: CVE-2025-40048

Detections

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