Emergency Flatpak fixes released: full sandbox escape possible
It’s not the first time sandboxes prove to have no boundaries.
Image by Cybernews.
- Flatpak fixed a critical flaw allowing malicious sandboxed apps to access host files and potentially execute code.
- Version 1.18.1 addresses ten vulnerabilities, including bugs enabling root access, file changes, and vulnerable app downgrades.
- All older Flatpak versions may be vulnerable; maintainers urge users to install version 1.18.1 or prerelease 1.19.0.
- Major distributions including Fedora had not yet delivered version 1.18.1, leaving users exposed until updates arrive.
Flatpak, one of the main ways Linux users get their applications, has disclosed several vulnerabilities, including a critical one that enables a sandbox escape with full host access.
Flatpak is a universal software tool for Linux that lets users install desktop apps with all required dependencies and run them isolated from the rest of the system.
However, a critical vulnerability enables a malicious sandboxed app to obtain arbitrary read and write access to files on the host, which can be further escalated to arbitrary code execution, an advisory on GitHub warns.
The issue arises because of missing symlink protection. Flatpak apps have their own private directories, but attackers can replace them with symlinks – basically shortcuts – pointing to different parts of the computer, like the user’s home folder, and Flatpak doesn’t check for this.
“A malicious symlink can point to arbitrary locations on the host, and it will become mounted inside the sandbox,” the advisory reads.
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Multiple other vulnerabilities were also fixed with the Flatpak 1.18.1 release. Nine other severe Flatpak vulnerabilities were also addressed, according to a post on the oss-security mailing list.
Path traversal bugs allow attackers to escalate privileges to root, enable arbitrary root file writes/reads, downgrade system apps to known older vulnerable versions, and more.
“All older Flatpak versions are believed to be vulnerable to all of these,” the post warns.
“If possible, please upgrade to the latest stable release, 1.18.1. For users of development prereleases, the 1.19.0 prerelease also fixes the same vulnerabilities.”
Major Linux distributions that bundle Flatpak by default, such as Fedora, have yet to push the latest version 1.18.1 to their stable releases.
CVE IDs have been requested for all ten vulnerabilities – two of the pack have been assigned CVE numbers by Red Hat.
Flatpack sandbox escape bugs have been identified before. One of the most serious ones, CVE-2026-34078, was disclosed in April and has a perfect 10 out of 10 severity score, according to the National Vulnerability Database.