Unity Linux 20.1050e Security Update: kernel (UTSA-2026-100173)

high Nessus Plugin ID 336433

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-2026-100173 advisory.

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

netfilter: bridge: make ebt_snat ARP rewrite writable

The ebtables SNAT target keeps the Ethernet source address rewrite behind skb_ensure_writable(skb, 0). This is intentional: at the bridge ebtables hooks the Ethernet header is addressed through skb_mac_header()/eth_hdr(), while skb->data points at the Ethernet payload. Asking skb_ensure_writable() for ETH_HLEN bytes would check the payload, not the Ethernet header, and would reintroduce the small packet regression fixed by commit 63137bc5882a.

However, the optional ARP sender hardware address rewrite is different.
It writes through skb_store_bits() at an offset relative to skb->data:

skb_store_bits(skb, sizeof(struct arphdr), info->mac, ETH_ALEN)

skb_header_pointer() only safely reads the ARP header; it does not make the later sender hardware address range writable. If that range is still held in a nonlinear skb fragment backed by a splice-imported file page, skb_store_bits() maps the frag page and copies the new MAC address directly into it.

Ensure the ARP SHA range is writable before reading the ARP header and before calling skb_store_bits().

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: 336433

File Name: unity_linux_UTSA-2026-100173.nasl

Version: 1.3

Type: Local

Family: Unity Linux Local Security Checks

Published: 8/17/2026

Updated: 9/18/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Critical

Score: 9.3

Percentile: 99.82

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5.6

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

CVSS Score Source: CVE-2026-53266

CVSS v3

Risk Factor: High

Base Score: 8.8

Temporal Score: 8.2

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

Temporal Vector: CVSS:3.0/E:F/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 Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 8/13/2026

Vulnerability Publication Date: 6/25/2026

CISA Known Exploited Vulnerability Due Dates: 9/21/2026

Reference Information

CVE: CVE-2026-53266

Detections

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