KDE Arianna EUVD-2026-25566

Exploitation requires local system access (AV:L confirmed by CVSS vector) and does not require elevated privileges (PR:N). The attacker must have the ability to connect to the bookserver socket, which is typically only accessible to the user running Arianna or, in some configurations, other local users depending on socket file permissions. No special configuration or non-default settings are required; the vulnerability exists in the default bookserver implementation. User interaction is not required (UI:N). The vulnerability is confined to the bookserver component and does not affect other Arianna features or the wider system.

The risk profile is constrained despite the authentication bypass nature: CVSS score of 4.0 reflects low overall severity due to local-only attack vector (AV:L), no privilege escalation (PR:N suggests unprivileged local access suffices), and confidentiality-only impact (C:L, no integrity or availability loss). EPSS data not provided, limiting probability assessment. No KEV confirmation or public exploit code identified, suggesting this is a discovered-but-not-weaponized vulnerability. The real-world risk depends on system exposure: on multi-user systems or containers where untrusted local users exist, this becomes more concerning; on single-user desktops, risk is minimal. The authentication bypass is high-severity in principle (CWE-306 is critical), but the local-only constraint and file-read-only impact keep practical risk moderate. Defenders should treat this as a priority patch for shared-access systems but not an emergency for single-user deployments.

A local user on a shared system connects directly to Arianna's bookserver socket (typically via a Unix domain socket in /tmp or user runtime directory) and guesses or enumerates file paths-for example, requesting /etc/passwd or ~/.ssh/id_rsa-without providing authentication. The unvalidated socket listener returns the requested file content, allowing the attacker to read sensitive configuration, credentials, or personal files stored on the system.