Unity Linux 20.1050a Security Update: kernel (UTSA-2026-146699)

critical Nessus Plugin ID 373091

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-2026-146699 advisory.

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

NFSD: check truncate permission under inode lock

nfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC before it takes inode_lock(). The comparison uses the file size sampled by that unlocked read, but the actual ATTR_SIZE update is applied later under inode_lock() by notify_change().

This leaves a TOCTOU window for append-only files. If a client sends a SETATTR that does not shrink the file at the time of the unlocked sample, a concurrent append can extend the file before nfsd_setattr() takes inode_lock(). notify_change() then applies a real truncation without the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS truncate syscall paths perform their own append-only checks before calling notify_change(), so NFSD must make this decision against the locked size it is about to change.

Split the write-count acquisition from the truncation permission check.
Keep get_write_access() before the locked setattr work, then recheck whether the requested size is below i_size_read(inode) after inode_lock() has been acquired and before notify_change(ATTR_SIZE). This also avoids the plain unlocked inode->i_size load.

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: Critical

ID: 373091

File Name: unity_linux_UTSA-2026-146699.nasl

Version: 1.1

Type: Local

Family: Unity Linux Local Security Checks

Published: 10/28/2026

Updated: 10/28/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.3

Percentile: 53.49

CVSS v2

Risk Factor: High

Base Score: 9.4

Temporal Score: 7

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

CVSS Score Source: CVE-2026-89713

CVSS v3

Risk Factor: Critical

Base Score: 9.1

Temporal Score: 7.9

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

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Required KB Items: Host/local_checks_enabled, Host/UOS-Server/release, Host/UOS-Server/rpm-list, Host/cpu

Exploit Ease: No known exploits are available

Patch Publication Date: 10/28/2026

Vulnerability Publication Date: 9/11/2026

Reference Information

CVE: CVE-2026-89713

Detections

Analytics