Amazon Linux 2023 : flatpak, flatpak-devel, flatpak-libs (ALAS2023-2026-3143)

high Nessus Plugin ID 351027

Synopsis

The remote Amazon Linux 2023 host is missing a security update.

Description

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-3143 advisory.

A flaw was found in Flatpak. A Time-of-check to time-of-use (TOCTOU) race condition exists in the `org.freedesktop.Flatpak.SystemHelper` component. This vulnerability occurs because a privileged `chmod` operation executes before the OSTree repository validation within the `Deploy()` function. An attacker can exploit this timing window to redirect symlinks to arbitrary files, potentially leading to unauthorized file manipulation or information disclosure. (CVE-2026-76925)

In Flatpak before 1.18.1, a malicious sandboxed app can obtain arbitrary read and write access to files on the host, which can be escalated to arbitrary code execution on the host, a different vulnerability than CVE-2026-76925. Flatpak creates a few app data directories (e.g., /var/cache, /var/data, /var/config, and /var/tmp) in every sandbox on every app launch where, in some cases, components of the path are attacker- controlled. Missing symlink protection can redirect the directories. Some of these directories are bind- mounted by Flatpak by passing the path (e.g., /home/user/.var/app/APP_ID/cache/tmp), which contains attacker-controlled directories (tmp) to bwrap --bind SRC DST. bwrap passes the path on to the kernel, which then follows symlinks. A malicious symlink can point to arbitrary locations on the host and it will become mounted inside the sandbox. (CVE-2026-90616)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Run 'dnf update flatpak --releasever 2023.12.20260928' or or 'dnf update --advisory ALAS2023-2026-3143 --releasever 2023.12.20260928' to update your system.

Plugin Details

Severity: High

ID: 351027

File Name: al2023_ALAS2023-2026-3143.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 9/29/2026

Updated: 9/29/2026

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Continuous Assessment, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.9

Percentile: 96.53

CVSS v2

Risk Factor: Medium

Base Score: 6.2

Temporal Score: 4.6

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

CVSS Score Source: CVE-2026-90616

CVSS v3

Risk Factor: High

Base Score: 7.4

Temporal Score: 6.4

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

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

Vulnerability Information

CPE: cpe:/o:amazon:linux:2023, p-cpe:/a:amazon:linux:flatpak-debuginfo, p-cpe:/a:amazon:linux:flatpak-debugsource, p-cpe:/a:amazon:linux:flatpak-devel, p-cpe:/a:amazon:linux:flatpak-libs-debuginfo, p-cpe:/a:amazon:linux:flatpak-libs, p-cpe:/a:amazon:linux:flatpak-selinux, p-cpe:/a:amazon:linux:flatpak-session-helper-debuginfo, p-cpe:/a:amazon:linux:flatpak-session-helper, p-cpe:/a:amazon:linux:flatpak-tests-debuginfo, p-cpe:/a:amazon:linux:flatpak-tests, p-cpe:/a:amazon:linux:flatpak

Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 9/29/2026

Vulnerability Publication Date: 9/4/2026

Reference Information

CVE: CVE-2026-76925, CVE-2026-90616

IAVA: 2026-A-0990

Detections

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