Misskey EUVD-2026-52449

The attacker requires network-level HTTP access to a Misskey instance running versions 2024.5.0 through 2026.5.3. No authentication is required per the CVSS PR:N metric. The CVSS 4.0 AT:P metric indicates a specific attack prerequisite exists outside the attacker's direct control - the exact nature of this prerequisite is not specified in the available advisory text, and operators should consult the vendor advisory for clarification. Exploitation is not restricted to federated deployments; self-hosted, non-federated instances are equally affected per the advisory. Impact is strictly limited to low-level confidentiality disclosure from the Announcements API: no integrity or availability compromise is possible, which materially limits the worst-case outcome of successful exploitation.

The CVSS 4.0 score of 6.3 reflects a network-accessible (AV:N), low-complexity (AC:L) vulnerability requiring no privileges (PR:N) or user interaction (UI:N), but with only low confidentiality impact on the vulnerable system (VC:L) and no integrity or availability impact. The AT:P metric introduces a specific prerequisite condition outside attacker control, which moderates the risk relative to a fully unconstrained flaw. Real-world risk is moderate: the exposure is limited to unauthorized read access of announcement data - which may contain sensitive administrative communications or internal metadata - and does not facilitate code execution, privilege escalation, or account compromise. No EPSS data was available in the provided input; KEV status is unconfirmed and no public exploit code has been identified at time of analysis, suggesting this has not yet attracted widespread automated exploitation. Internet-facing Misskey instances should prioritize patching; the risk to air-gapped or strictly internal deployments is considerably lower.

An unauthenticated remote attacker crafts HTTP requests targeting the Server Announcements API on a vulnerable Misskey instance (versions 2024.5.0-2026.5.3), bypassing the absent or insufficient permission check to retrieve announcement data intended for restricted audiences. No public exploit code exists at time of analysis, but the network-accessible, no-authentication-required vector means any attacker with HTTP connectivity to the instance can attempt exploitation without specialized tooling.