CVE-2026-96275

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.

Red Hat estimates the CVSSv3.1 vector of CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

Exploitation requires a user or administrator to add or trust a malicious or compromised Flatpak repository and then install or update an application from it. The malicious content is served over the network (AV:N), and the attacker needs only control over the repository content (PR:N). Once the client pulls from that repository, exploitation is deterministic and requires no race condition or additional preconditions: extract_extra_data() resolves files/extra inside the checked-out commit tree using path operations that follow symlinks, so a files entry that is itself a symlink (e.g., files -> /tmp) redirects the write; separately, the blob name taken from xa.extra-data-sources is not sanitized against .. traversal, allowing it to escape the extra/ directory (AC:L). Meaningful user interaction is required, since a user/admin must actively configure the remote and initiate an install or update from it (UI:R).

On system-wide installs, this extraction runs via the privileged system-helper, so the write happens as root (S:U reflects that the vulnerable and impacted components remain within the same overall flatpak client/helper security authority, which by design already operates with root privileges for system installs). Because this is an unconstrained, attacker-controlled write as root, it is treated as equivalent to full system compromise: an attacker can overwrite files such as SSH authorized_keys, systemd units, cron entries, or setuid binaries, yielding full loss of confidentiality, integrity, and availability (C:H/I:H/A:H).

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Avoid installing Flatpak extensions from non-trusted sources.