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Ubuntu 18.04 LTS / 20.04 LTS : Flatpak vulnerability (USN-4951-1)

high Nessus Plugin ID 149404

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Synopsis

The remote Ubuntu host is missing a security update.

Description

The remote Ubuntu 18.04 LTS / 20.04 LTS / 20.10 host has packages installed that are affected by a vulnerability as referenced in the USN-4951-1 advisory.

 - Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. In Flatpack since version 0.9.4 and before version 1.10.2 has a vulnerability in the file forwarding feature which can be used by an attacker to gain access to files that would not ordinarily be allowed by the app's permissions. By putting the special tokens `@@` and/or `@@u` in the Exec field of a Flatpak app's .desktop file, a malicious app publisher can trick flatpak into behaving as though the user had chosen to open a target file with their Flatpak app, which automatically makes that file available to the Flatpak app. This is fixed in version 1.10.2. A minimal solution is the first commit `Disallow @@ and @@U usage in desktop files`. The follow-up commits `dir: Reserve the whole @@ prefix` and `dir: Refuse to export .desktop files with suspicious uses of @@ tokens` are recommended, but not strictly required. As a workaround, avoid installing Flatpak apps from untrusted sources, or check the contents of the exported `.desktop` files in `exports/share/applications/*.desktop` (typically `~/.local/share/flatpak/exports/share/applications/*.desktop` and `/var/lib/flatpak/exports/share/applications/*.desktop`) to make sure that literal filenames do not follow `@@` or `@@u`. (CVE-2021-21381)

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 packages.

See Also

https://ubuntu.com/security/notices/USN-4951-1

Plugin Details

Severity: High

ID: 149404

File Name: ubuntu_USN-4951-1.nasl

Version: 1.4

Type: local

Agent: unix

Published: 5/12/2021

Updated: 10/16/2023

Supported Sensors: Agentless Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Frictionless Assessment Azure, Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: High

Score: 7.1

CVSS v2

Risk Factor: Medium

Base Score: 5.8

Temporal Score: 4.3

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

CVSS Score Source: CVE-2021-21381

CVSS v3

Risk Factor: High

Base Score: 8.2

Temporal Score: 7.1

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

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

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:18.04:-:lts, cpe:/o:canonical:ubuntu_linux:20.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:flatpak, p-cpe:/a:canonical:ubuntu_linux:flatpak-tests, p-cpe:/a:canonical:ubuntu_linux:gir1.2-flatpak-1.0, p-cpe:/a:canonical:ubuntu_linux:libflatpak-dev, p-cpe:/a:canonical:ubuntu_linux:libflatpak0

Required KB Items: Host/cpu, Host/Ubuntu, Host/Ubuntu/release, Host/Debian/dpkg-l

Exploit Ease: No known exploits are available

Patch Publication Date: 5/12/2021

Vulnerability Publication Date: 3/10/2021

Reference Information

CVE: CVE-2021-21381

USN: 4951-1