flatpak vulnerabilities

Flatpak vulnerable to path traversal via unvalidated "arch" parameter in DeployAppstream

Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. Prior to version 1.18.1, on systems where at least one OCI remote is configured (most common on Fedora systems), a malicious local user in an active local session could use a crafted architecture name to trick the `flatpak-system-helper` process into creating a root-owned directory tree with contents determined by the OCI remote, plus a root-owned `lock` file and `icons` directory, outside the intended root directory. If this vulnerability is combined with other vulnerabilities also fixed in 1.18.1, the combination can lead to local root privi

Flatpak: flatpak: sandboxed app can signal unsandboxed processes in the same process group

Flatpak's process ID namespace separation does not prevent a sandboxed app's kill(0, signal) or killpg(0, signal) calls from reaching processes outside the sandbox that share the same process group. A malicious or compromised Flatpak app can use this to cause denial of service by terminating processes outside its sandbox, such as the desktop shell.

Flatpak: flatpak: arbitrary write in root context via path traversal in deploy directory files/etc

A path traversal vulnerability in Flatpak's handling of the files/etc directory during app deployment allows a malicious Flatpak app to cause certain host system files (such as passwd, group, machine-id, or resolv.conf) to be emptied or replaced with a symlink when the app is installed or upgraded. In system-wide installations, the write is performed as root.

Flatpak: flatpak: denial of service via unsanitized keys in exported desktop entry / d-bus service files

Flatpak passes through arbitrary vendor-extension keys unmodified when exporting an application's Desktop Entry (.desktop) and D-Bus Service (.service) files, instead of validating against an allowlist. A malicious Flatpak app can use this to cause denial of service (e.g. forced application restart loops) or to influence host D-Bus/systemd activation behavior beyond what the sandbox is intended to permit.

Flatpak: flatpak: world-writable temporary child repositories in system-helper cache path

Flatpak creates temporary child repository directories under the user cache with world-writable permissions (0777). On multi-user systems with a permissive umask, other local users could read or modify the temporary directory used while installing apps or runtimes, potentially causing installation failures (denial of service); tampered content would fail signature/digest verification rather than being trusted.

Flatpak: flatpak: world-readable oci authentication token in system-helper cache path

Flatpak writes the OCI repository authentication token with world-readable permissions (0644) in the system-helper's cache directory, allowing other local users on a multi-user system to read the token and impersonate the authenticated user against the OCI repository. Only OCI-based sources (e.g. as used by Fedora) are affected; libostree-based sources such as Flathub are not.

Flatpak: flatpak: arbitrary file deletion in root context via path traversal in deploy directory export/bin

A path traversal vulnerability in Flatpak's handling of the export/bin directory during app deployment allows a malicious Flatpak app to cause deletion of attacker-chosen files outside the deployment directory when the app is installed or upgraded. In system-wide installations, the deletion is performed as root.

Flatpak: flatpak: arbitrary read-access to files in the system-helper context via oci symlink following

A malicious user can get read-access to files in the flatpak-system-helper context if a system OCI repository is configured, because the OCI code paths in the system helper follow symlinks when importing OCI images that are under the user's control.

• Update to 1.14.10-1~deb12u2

Flatpak: flatpak: extension metadata path traversal file existence oracle

A malicious Flatpak extension can probe the host filesystem to determine what files and directories exist at arbitrary paths, and host directory listings can be disclosed to sandboxed applications using the extension. Additionally, unvalidated extension metadata can cause extension content to be mounted at unintended locations inside the sandbox.

Flatpak: flatpak: flatpak-system-helper cross-user cancelpull orphans another user's ongoing pull

By calling org.freedesktop.Flatpak.SystemHelper.CancelPull on another user's pull, the pull is not actually cancelled but removed from internal tracking, making it impossible for the owning user to stop it. Ongoing pulls cannot be stopped.

• Update to 1.14.10-1~deb12u2

Flatpak: flatpak: unprivileged active user can bypass anti-downgrade checks for system apps/runtimes

On a multi-user system, a user with an active local login session could downgrade a system-wide Flatpak app to an older version by removing the app's remote ref via the unprivileged system-helper RemoveLocalRef method, causing the anti-downgrade check to fail to find a reference date. A malicious local user could use this to expose other users of the same system to an app version with unfixed vulnerabilities.

Flatpak: flatpak: buffer overflow in oci delta stream path names on 32-bit systems

The OCI delta stream parser read sizes as guint64 but passed them to GLib I/O and allocation functions expecting gsize (32 bits on 32-bit systems), causing undersized allocations while subsequent operations use the original 64-bit size, leading to heap buffer overflows. An attacker controlling an OCI registry can craft a delta stream that triggers this during flatpak install/update, potentially achieving code execution on 32-bit systems.

CVE-2026-96808

In Flatpak before 1.18.1, the revokefs writer, used by the flatpak-system-helper to receive repository data from unprivileged callers, validated file paths by rejecting literal .. components but did not prevent symlink traversal. A malicious local user in an active local session could obtain two revokefs sessions via the system helper, create a symlink in one session pointing into the other session's directory, and retain a file descriptor through that symlink. This allowed the attacker to modify files belonging to a different revokefs session after they had been validated and imported by the system helper. In particular, an attacker could us

CVE-2026-96807

In Flatpak before 1.18.1, a malicious sandboxed app can replace ~/.var/app/$appid/.ld.so with a symlink, causing regenerate_ld_cache to write files at an arbitrary location. The filenames and content are not attacker controlled, making this hard to exploit.

Flatpak: flatpak: arbitrary write in host context via flatpak build-init

If a malicious SDK container declares an extension point with a crafted `directory` path, and a developer runs `flatpak build-init --writable-sdk --sdk-extension` with that SDK, attacker-chosen files could be written outside the working directory, since the target path is resolved via a function that allows `..` traversal.

Flatpak: flatpak: arbitrary write access as root via extra-data extraction

A malicious or compromised Flatpak repository can write attacker-controlled content to arbitrary locations on the host filesystem via extract_extra_data(). On system installs, the write happens as root. Two issues combine: `files/extra` is resolved via path operations that follow symlinks, and blob names from `xa.extra-data-sources` are not sanitized against `..` traversal.

CVE-2026-90616

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 dir

Flatpak affected by arbitrary file deletion on the host filesystem

Flatpak is a Linux application sandboxing and distribution framework. Prior to 1.16.4, the caching for ld.so removes outdated cache files without properly checking that the app controlled path to the outdated cache is in the cache directory. This allows Flatpak apps to delete arbitrary files on the host. This vulnerability is fixed in 1.16.4.

• Update to 1.14.10-1~deb12u2

Flatpak has a complete sandbox escape leading to host file access and code execution in the host context

Flatpak is a Linux application sandboxing and distribution framework. Prior to 1.16.4, the Flatpak portal accepts paths in the sandbox-expose options which can be app-controlled symlinks pointing at arbitrary paths. Flatpak run mounts the resolved host path in the sandbox. This gives apps access to all host files and can be used as a primitive to gain code execution in the host context. This vulnerability is fixed in 1.16.4.

• Update to 1.14.10-1~deb12u2

Flatpak may allow access to files outside sandbox for certain apps

Flatpak is a Linux application sandboxing and distribution framework. Prior to versions 1.14.0 and 1.15.10, a malicious or compromised Flatpak app using persistent directories could access and write files outside of what it would otherwise have access to, which is an attack on integrity and confidentiality. When `persistent=subdir` is used in the application permissions (represented as `--persist=subdir` in the command-line interface), that means that an application which otherwise doesn't have access to the real user home directory will see an empty home directory with a writeable subdirectory `subdir`. Behind the scenes, this directory is

• Update to 1.14.10-1~deb12u1