CVE-2026-46712: Misskey Information Disclosure Flaw

CVE-2026-46712 Overview

CVE-2026-46712 affects Misskey, an open source federated social media platform. The vulnerability stems from missing permission checks in the Direct Messages feature, formerly known as Chat. Affected versions expose certain data points from Direct Messages regardless of account permissions. The issue affects instances whether or not federation is enabled. Notes created with specified visibility, formerly direct visibility, are not affected. The flaw is tracked under [CWE-639: Authorization Bypass Through User-Controlled Key].

Critical Impact
Authenticated users can access limited Direct Message data points without the proper account permissions, resulting in unauthorized information disclosure on affected Misskey instances.

Affected Products

Misskey versions 2025.3.2 and later
Misskey versions prior to 2026.5.4
Misskey federated and non-federated deployments

Discovery Timeline

2026-08-03 - CVE CVE-2026-46712 published to NVD
2026-08-04 - Last updated in NVD database
Version 2026.5.4 - Fixed release published by Misskey maintainers

Technical Details for CVE-2026-46712

Vulnerability Analysis

Misskey's Direct Messages feature exposes data endpoints without validating whether the requesting account holds the permissions required to view that data. The server-side authorization layer does not enforce ownership or participation checks on certain Direct Message data points. As a result, authenticated clients can retrieve information they should not be able to see.

The vulnerability is limited in scope. It exposes select data points rather than full message contents across all conversations. Notes published with specified visibility, the successor of the older direct visibility mode, use a separate access path and are unaffected.

Root Cause

The root cause is a broken access control pattern in the Direct Messages code path. Requests to certain endpoints proceed based on request parameters rather than a server-side check binding the resource to the caller's identity. This matches the pattern described in [CWE-639], where authorization is skipped or performed against user-controlled keys.

Attack Vector

Exploitation requires network access to a vulnerable Misskey instance and valid low-privilege credentials on that instance. An authenticated attacker can query the affected Direct Message endpoints and receive data belonging to conversations they are not a participant in. Federation status does not change the outcome, so both federated and standalone deployments are affected. See the GitHub Security Advisory GHSA-2m3r-xx7x-63j6 for advisory details.

No public proof-of-concept, exploit tooling, or CISA KEV listing is currently associated with this CVE.

Detection Methods for CVE-2026-46712

Indicators of Compromise

Unexpected read traffic from low-privilege accounts to Direct Message API endpoints on the Misskey instance.
API access logs showing a single account querying Direct Message resource identifiers it does not participate in.
Sudden spikes in authenticated requests to chat-related routes from a small number of accounts.

Detection Strategies

Review Misskey application logs and reverse proxy logs for repeated Direct Message API calls from the same authenticated session.
Correlate account activity with conversation membership records to surface reads outside expected participants.
Alert on abnormal enumeration patterns against Direct Message identifiers, such as sequential or high-volume access.

Monitoring Recommendations

Ingest Misskey and reverse proxy access logs into a centralized logging pipeline for retention and query.
Baseline normal Direct Message API usage per account and alert on deviations.
Track the deployed Misskey version across all instances and flag any host still running a version between 2025.3.2 and 2026.5.4.

How to Mitigate CVE-2026-46712

Immediate Actions Required

Upgrade Misskey to version 2026.5.4 or later on all affected instances.
Audit Direct Message API access logs for the period since 2025.3.2 was deployed to identify potential unauthorized reads.
Rotate session tokens and require reauthentication if suspicious access is observed.

Patch Information

The issue is fixed in Misskey 2026.5.4. Release notes and downloadable artifacts are available at the GitHub Misskey Release 2026.5.4 page. Operators running any version from 2025.3.2 up to but not including 2026.5.4 must upgrade.

Workarounds

No official workaround is documented; upgrading to 2026.5.4 is the recommended remediation.
If upgrade must be delayed, restrict account registration and limit access to the instance to trusted users only.
Consider temporarily disabling the Direct Messages feature via administrative controls if that option is available in your deployment.

bash

# Example upgrade steps for a self-hosted Misskey instance
git fetch --tags
git checkout 2026.5.4
pnpm install
pnpm run build
pnpm run migrate
systemctl restart misskey