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Unity Linux 20.1070a Security Update: kernel (UTSA-2025-986281)

medium Nessus Plugin ID 268097

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-2025-986281 advisory.

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

 powerpc/64s: Fix crashes when toggling entry flush barrier

 The entry flush mitigation can be enabled/disabled at runtime via a debugfs file (entry_flush), which causes the kernel to patch itself to enable/disable the relevant mitigations.

 However depending on which mitigation we're using, it may not be safe to do that patching while other CPUs are active. For example the following crash:

 sleeper[15639]: segfault (11) at c000000000004c20 nip c000000000004c20 lr c000000000004c20

 Shows that we returned to userspace with a corrupted LR that points into the kernel, due to executing the partially patched call to the fallback entry flush (ie. we missed the LR restore).

 Fix it by doing the patching under stop machine. The CPUs that aren't doing the patching will be spinning in the core of the stop machine logic. That is currently sufficient for our purposes, because none of the patching we do is to that code or anywhere in the vicinity.

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.

See Also

http://www.nessus.org/u?f57724c4

http://www.nessus.org/u?aa20f4fe

https://nvd.nist.gov/vuln/detail/CVE-2021-46990

Plugin Details

Severity: Medium

ID: 268097

File Name: unity_linux_UTSA-2025-986281.nasl

Version: 1.1

Type: local

Published: 10/7/2025

Updated: 10/7/2025

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v2

Risk Factor: Medium

Base Score: 4.6

Temporal Score: 3.4

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

CVSS Score Source: CVE-2021-46990

CVSS v3

Risk Factor: Medium

Base Score: 5.5

Temporal Score: 4.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/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: 9/22/2025

Vulnerability Publication Date: 2/28/2024

Reference Information

CVE: CVE-2021-46990