Unity Linux 20.1050e Security Update: kernel (UTSA-2026-102135)

high Nessus Plugin ID 337291

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-2026-102135 advisory.

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

netfilter: nft_ct: add seqadj extension for natted connections

Sequence adjustment may be required for FTP traffic with PASV/EPSV modes.
due to need to re-write packet payload (IP, port) on the ftp control connection. This can require changes to the TCP length and expected seq / ack_seq.

The easiest way to reproduce this issue is with PASV mode.
Example ruleset:
table inet ftp_nat { ct helper ftp_helper { type ftp protocol tcp l3proto inet }

chain prerouting { type filter hook prerouting priority 0; policy accept;
tcp dport 21 ct state new ct helper set ftp_helper } } table ip nat { chain prerouting { type nat hook prerouting priority -100; policy accept;
tcp dport 21 dnat ip prefix to ip daddr map { 192.168.100.1 : 192.168.13.2/32 } }

chain postrouting { type nat hook postrouting priority 100 ; policy accept;
tcp sport 21 snat ip prefix to ip saddr map { 192.168.13.2 : 192.168.100.1/32 } } }

Note that the ftp helper gets assigned *after* the dnat setup.

The inverse (nat after helper assign) is handled by an existing check in nf_nat_setup_info() and will not show the problem.

Topoloy:

+-------------------+ +----------------------------------+ | FTP: 192.168.13.2 | <-> | NAT: 192.168.13.3, 192.168.100.1 | +-------------------+ +----------------------------------+ | +-----------------------+ | Client: 192.168.100.2 | +-----------------------+

ftp nat changes do not work as expected in this case:
Connected to 192.168.100.1.
[..] ftp> epsv EPSV/EPRT on IPv4 off.
ftp> ls 227 Entering passive mode (192,168,100,1,209,129).
421 Service not available, remote server has closed connection.

Kernel logs:
Missing nfct_seqadj_ext_add() setup call WARNING: CPU: 1 PID: 0 at net/netfilter/nf_conntrack_seqadj.c:41 [..]
__nf_nat_mangle_tcp_packet+0x100/0x160 [nf_nat] nf_nat_ftp+0x142/0x280 [nf_nat_ftp] help+0x4d1/0x880 [nf_conntrack_ftp] nf_confirm+0x122/0x2e0 [nf_conntrack] nf_hook_slow+0x3c/0xb0 ..

Fix this by adding the required extension when a conntrack helper is assigned to a connection that has a nat binding.

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: 337291

File Name: unity_linux_UTSA-2026-102135.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: Low

Score: 3

Percentile: 23.43

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-2025-68206

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: 12/16/2025

Reference Information

CVE: CVE-2025-68206

Detections

Analytics