CVE-2026-90616
Received Received - Intake

Arbitrary File Access via Symlink in Flatpak

Publication date: 2026-09-12

Last updated on: 2026-09-12

Assigner: MITRE

Description
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.

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Meta Information

Published
2026-09-12
Last Modified
2026-09-12
Generated
2026-09-13
AI Q&A
2026-09-12
EPSS Evaluated
N/A
NVD
CVE-2026-90616

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
flatpak flatpak to 1.18.0 (inc)
flatpak flatpak 1.18.1
flatpak flatpak 1.19.0
flatpak flatpak 1.16.x

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-61 The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.

Attack-Flow Graph

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Executive Summary

This vulnerability in Flatpak before 1.18.1 allows a malicious sandboxed app to bypass symlink protections and gain arbitrary read and write access to files on the host system. The issue occurs because Flatpak creates app data directories with attacker-controlled path components, which can be redirected via symlinks to arbitrary host locations. These directories are then bind-mounted into the sandbox, enabling the app to access sensitive host files or escalate to arbitrary code execution.

Detection Guidance

Check Flatpak version with 'flatpak --version'. If it is below 1.18.1, the system is vulnerable. Inspect sandboxed app directories for unexpected symlinks or unusual file access patterns in /var/cache, /var/data, /var/config, or /var/tmp.

Impact Analysis

If you run a vulnerable version of Flatpak, a malicious app you install could read or modify sensitive files on your host system, including system files or user data. This could lead to data theft, system compromise, or further attacks like installing malware. The impact is severe as it breaks the sandboxing intended to isolate apps from the host.

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating compliance requirements like GDPR (data protection) or HIPAA (health information privacy). Organizations using vulnerable Flatpak versions may face legal penalties, reputational damage, or loss of certification if data breaches occur due to this flaw.

Mitigation Strategies

Upgrade Flatpak to version 1.18.1 or later immediately. If upgrading is not possible, apply backported fixes for older versions like 1.16.x. Avoid running untrusted Flatpak applications until patched.

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