CVE-2026-97025: Flatpak Token Exposure Vulnerability

CVE-2026-97025 Overview

CVE-2026-97025 is an insecure file permissions vulnerability in Flatpak, the Linux application sandboxing and distribution framework. The flatpak system-helper writes Open Container Initiative (OCI) repository authentication tokens to its cache directory with world-readable permissions (0644). Any local user on a multi-user system can read the token and impersonate the authenticated user against the OCI repository. Only OCI-based sources such as those used by Fedora are affected. Libostree-based sources such as Flathub are not affected. The issue is tracked under [CWE-378: Creation of Temporary File With Insecure Permissions].

Critical Impact
A local unprivileged user can read another user's OCI repository authentication token from the Flatpak system-helper cache and reuse it to impersonate that user against the repository.

Affected Products

Flatpak (system-helper component) on multi-user Linux systems
Deployments using OCI-based Flatpak sources (for example, Fedora)
Libostree-based sources such as Flathub are not affected

Discovery Timeline

2026-09-28 - CVE-2026-97025 published to NVD
2026-09-29 - Last updated in NVD database

Technical Details for CVE-2026-97025

Vulnerability Analysis

Flatpak splits privileged operations between an unprivileged client and a flatpak-system-helper D-Bus service running as root. When the system-helper interacts with an OCI-based remote, it caches the authentication token returned by the registry. The cache file is written with mode 0644, granting read access to every local account. Any user on the host can read the cached bearer token and issue authenticated requests to the OCI repository as the victim. Impact is limited to confidentiality of the token and any actions the token authorizes against the remote registry. Integrity and availability of the local Flatpak installation are unaffected.

Root Cause

The defect stems from the system-helper creating cache files with default umask-derived permissions instead of restricting access to the owning user. Sensitive credential material stored under the cache directory inherits 0644 mode, exposing it to unrelated local users. This maps to CWE-378, where a file containing sensitive data is created with permissions broader than required.

Attack Vector

Exploitation requires local access with an unprivileged account on a shared host where another user has authenticated to an OCI-based Flatpak remote. The attacker enumerates the system-helper cache directory, reads the world-readable token file, and replays the bearer token to the OCI registry. No user interaction from the victim is required beyond having previously authenticated. The vulnerability does not enable local privilege escalation or code execution on the host itself. See the GitHub Flatpak Security Advisory and the Red Hat CVE-2026-97025 Advisory for vendor detail.

Detection Methods for CVE-2026-97025

Indicators of Compromise

Files under the flatpak-system-helper cache directory containing OCI bearer tokens with mode 0644.
Unexpected reads of Flatpak system-helper cache files by user accounts that do not own them.
OCI registry access logs showing requests from IP addresses or client identifiers that do not match the authenticated user's normal activity.

Detection Strategies

Audit file modes across /var/cache and Flatpak system-helper working directories for token files not restricted to 0600.
Enable Linux audit rules (auditd) on the Flatpak system-helper cache path to record open and read operations by non-owning UIDs.
Correlate OCI registry authentication logs with local user sessions to identify token reuse from unexpected sources.

Monitoring Recommendations

Alert on any process reading Flatpak cache files where the reader UID differs from the file owner UID.
Track installation and update of the flatpak package to confirm patched versions are deployed across the fleet.
Monitor for anomalous outbound traffic from user accounts to OCI registries used by Flatpak remotes.

How to Mitigate CVE-2026-97025

Immediate Actions Required

Apply vendor updates for Flatpak as soon as fixed packages are available from your distribution.
On Fedora and other OCI-source consumers, revoke and reissue any OCI repository tokens that were cached by an affected flatpak-system-helper on a multi-user host.
Restrict interactive local access on shared systems where Flatpak OCI remotes have been authenticated.

Patch Information

Refer to the Red Hat CVE-2026-97025 Advisory, the Red Hat Bug Report #2542628, and the GitHub Flatpak Security Advisory for fixed package versions and backport availability. The upstream fix constrains cache file permissions so tokens are readable only by the owning user.

Workarounds

Avoid authenticating to OCI-based Flatpak remotes on multi-user hosts until patched packages are installed.
Prefer libostree-based sources such as Flathub, which are not affected by this issue.
Manually tighten permissions on the Flatpak system-helper cache directory and any existing token files to mode 0600 and owner-only access, then re-authenticate.

bash

# Configuration example: restrict Flatpak system-helper cache to owner-only
sudo find /var/cache/flatpak -type f -exec chmod 0600 {} \;
sudo find /var/cache/flatpak -type d -exec chmod 0700 {} \;