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Unity Linux 20.1070e Security Update: kernel (UTSA-2025-987542)

medium Nessus Plugin ID 271009

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-2025-987542 advisory.

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

 seg6: fix the iif in the IPv6 socket control block

 When an IPv4 packet is received, the ip_rcv_core(...) sets the receiving interface index into the IPv4 socket control block (v5.16-rc4, net/ipv4/ip_input.c line 510):

 IPCB(skb)->iif = skb->skb_iif;

 If that IPv4 packet is meant to be encapsulated in an outer IPv6+SRH header, the seg6_do_srh_encap(...) performs the required encapsulation.
 In this case, the seg6_do_srh_encap function clears the IPv6 socket control block (v5.16-rc4 net/ipv6/seg6_iptunnel.c line 163):

 memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));

 The memset(...) was introduced in commit ef489749aae5 (ipv6: sr: clear IP6CB(skb) on SRH ip4ip6 encapsulation) a long time ago (2019-01-29).

 Since the IPv6 socket control block and the IPv4 socket control block share the same memory area (skb->cb), the receiving interface index info is lost (IP6CB(skb)->iif is set to zero).

 As a side effect, that condition triggers a NULL pointer dereference if commit 0857d6f8c759 (ipv6: When forwarding count rx stats on the orig netdev) is applied.

 To fix that issue, we set the IP6CB(skb)->iif with the index of the receiving interface once again.

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.

See Also

http://www.nessus.org/u?78a8f146

http://www.nessus.org/u?6dfa1714

https://nvd.nist.gov/vuln/detail/CVE-2021-47515

Plugin Details

Severity: Medium

ID: 271009

File Name: unity_linux_UTSA-2025-987542.nasl

Version: 1.1

Type: local

Published: 10/21/2025

Updated: 10/21/2025

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-2021-47515

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: 10/15/2025

Vulnerability Publication Date: 1/28/2022

Reference Information

CVE: CVE-2021-47515