Detections
Analytics

Unity Linux 20.1070e Security Update: kernel (UTSA-2025-986952)

medium Nessus Plugin ID 268729

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-2025-986952 advisory.

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

 net: vlan: fix underflow for the real_dev refcnt

 Inject error before dev_hold(real_dev) in register_vlan_dev(), and execute the following testcase:

 ip link add dev dummy1 type dummy ip link add name dummy1.100 link dummy1 type vlan id 100 ip link del dev dummy1

 When the dummy netdevice is removed, we will get a WARNING as following:

 ======================================================================= refcount_t: decrement hit 0; leaking memory.
 WARNING: CPU: 2 PID: 0 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0

 and an endless loop of:

 ======================================================================= unregister_netdevice: waiting for dummy1 to become free. Usage count = -1073741824

 That is because dev_put(real_dev) in vlan_dev_free() be called without dev_hold(real_dev) in register_vlan_dev(). It makes the refcnt of real_dev underflow.

 Move the dev_hold(real_dev) to vlan_dev_init() which is the call-back of ndo_init(). That makes dev_hold() and dev_put() for vlan's real_dev symmetrical.

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?cacb00a3

http://www.nessus.org/u?d3477dde

https://nvd.nist.gov/vuln/detail/CVE-2021-47555

Plugin Details

Severity: Medium

ID: 268729

File Name: unity_linux_UTSA-2025-986952.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-2021-47555

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: 9/23/2025

Vulnerability Publication Date: 1/28/2022

Reference Information

CVE: CVE-2021-47555