Flatpak
CVE-2021-21261
HIGH
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Input neutralization, injection prevention
|
| Impact | CVSS score of 8.8 (HIGH). Attack characteristics: local attack vector, low complexity, low privileges required, no user interaction not required. |
| Exploit ScenarioDerived | Successful exploitation could compromise the high-severity affected system. |
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Alert meAnalysisAI
Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. Rated high severity (CVSS 8.8), this vulnerability is low attack complexity.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.
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Technical ContextAI · show details
This vulnerability is classified under CWE-74. Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. A bug was discovered in the flatpak-portal service that can allow sandboxed applications to execute arbitrary code on the host system (a sandbox escape). This sandbox-escape bug is present in versions from 0.11.4 and before fixed versions 1.8.5 and 1.10.0. The Flatpak portal D-Bus service (flatpak-portal, also known by its D-Bus service name org.freedesktop.portal.Flatpak) allows apps in a Flatpak sandbox to launch their own subprocesses in a new sandbox instance, either with the same security settings as the caller or with more restrictive security settings. For example, this is used in Flatpak-packaged web browsers such as Chromium to launch subprocesses that will process untrusted web content, and give those subprocesses a more restrictive sandbox than the browser itself. In vulnerable versions, the Flatpak portal service passes caller-specified environment variables to non-sandboxed processes on the host system, and in particular to the flatpak run command that is used to launch the new sandbox instance. A malicious or compromised Flatpak app could set environment variables that are trusted by the flatpak run command, and use them to execute arbitrary code that is not in a sandbox. As a workaround, this vulnerability can be mitigated by preventing the flatpak-portal service from starting, but that mitigation will prevent many Flatpak apps from working correctly. This is fixed in versions 1.8.5 and 1.10.0. Affected products include: Flatpak, Debian Debian Linux.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. A bug was discovered in the flatpak-portal service that can allow sandboxed applications to execute arbitrary code on the host system (a sandbox escape). This sandbox-escape bug is present in versions from 0.11.4 and before fixed versions 1.8.5 and 1.10.0. The Flatpak portal D-Bus service (flatpak-portal, also known by its D-Bus service name org.freedesktop.portal.Flatpak) allows apps in a Flatpak sandbox to launch their own subprocesses in a new sandbox instance, either with the same security settings as the caller or with more restrictive security settings. For example, this is used in Flatpak-packaged web browsers such as Chromium to launch subprocesses that will process untrusted web content, and give those subprocesses a more restrictive sandbox than the browser itself. In vulnerable versions, the Flatpak portal service passes caller-specified environment variables to non-sandboxed processes on the host system, and in particular to the flatpak run command that is used to launch the new sandbox instance. A malicious or compromised Flatpak app could set environment variables that are trusted by the flatpak run command, and use them to execute arbitrary code that is not in a sandbox. As a workaround, this vulnerability can be mitigated by preventing the flatpak-portal service from starting, but that mitigation will prevent many Flatpak apps from working correctly. This is fixed in versions 1.8.5 and 1.10.0.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.
Affected Products (CPE)NVD
Sandbox escape in Flatpak versions prior to 1.16.4 allows applications to access arbitrary host filesystem paths and ach
Flatpak before 1.0.8, 1.1.x and 1.2.x before 1.2.4, and 1.3.x before 1.3.1 allows a sandbox bypass. Rated critical sever
In dbus-proxy/flatpak-proxy.c in Flatpak before 0.8.9, and 0.9.x and 0.10.x before 0.10.3, crafted D-Bus messages to the
Arbitrary file deletion in Flatpak versions prior to 1.16.4 allows sandboxed applications to delete files on the host sy
Message-filtering bypass in xdg-dbus-proxy before 0.1.9 lets a malicious or already-compromised sandboxed application -
Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. Rated high severity
Flatpak before 1.0.7, and 1.1.x and 1.2.x before 1.2.3, exposes /proc in the apply_extra script sandbox, which allows at
In Flatpak before 0.8.7, a third-party app repository could include malicious apps that contain files with inappropriate
Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. Rated high severity
Local privilege escalation to root in Flatpak before 1.18.1 lets an unprivileged user holding an active local session ab
Path traversal in Flatpak's app deployment handling of the exported files/etc directory allows a malicious Flatpak appli
Path traversal in Flatpak's handling of the export/bin directory during application deployment allows a malicious Flatpa
Exploit-DB