CVE-2025-54461 Overview
CVE-2025-54461 is an access control weakness in ChatLuck, a business chat and collaboration platform. The flaw resides in the Invitation of Guest Users feature, where the system does not enforce sufficiently granular access checks. An uninvited external user can register themselves as a guest user without going through the intended invitation workflow. The issue is classified under CWE-1220: Insufficient Granularity of Access Control and is exploitable over the network without authentication or user interaction.
Critical Impact
Unauthenticated attackers can self-register as guest users in ChatLuck, gaining access to guest-level features and content that should be restricted to invited participants.
Affected Products
- ChatLuck (business chat and collaboration product from NEOJAPAN)
- See the ChatLuck Support Document for the list of impacted versions
- See the JVN Security Advisory for coordinated disclosure details
Discovery Timeline
- 2025-10-16 - CVE-2025-54461 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-54461
Vulnerability Analysis
ChatLuck supports inviting external users as guests to participate in chats, file exchanges, and collaboration spaces. The guest registration flow is intended to be gated by an invitation issued by an authorized internal user. CVE-2025-54461 shows that the access control checks around this workflow are too coarse. The registration endpoint accepts guest sign-ups without verifying that the requester holds a valid, unconsumed invitation tied to the requested identity.
An unauthenticated attacker reaching the guest registration surface over the network can create a guest account outside of the invitation process. Once registered, the account carries the same permissions granted to legitimately invited guests. Exposure is limited to confidentiality of guest-accessible resources; integrity and availability of the platform are not directly impacted according to the CVSS vector.
Root Cause
The underlying weakness is CWE-1220: Insufficient Granularity of Access Control. The guest invitation feature enforces authorization at too broad a level and fails to bind account creation to a specific, verified invitation token or invited email address. Without that binding, the workflow cannot distinguish between an invited user completing registration and an uninvited party self-provisioning an account.
Attack Vector
The attack vector is network-based and requires no privileges or user interaction. An attacker locates a ChatLuck instance exposed to their network path, reaches the guest registration endpoint, and submits a registration request. Because the server does not require a matching invitation, the account is created and the attacker can authenticate as a guest user. No verified public proof-of-concept code is available; refer to the JVN Security Advisory for coordinated technical details.
Detection Methods for CVE-2025-54461
Indicators of Compromise
- Guest user accounts in ChatLuck that do not correspond to any invitation record in the administrative audit log.
- Guest registrations originating from unexpected IP ranges, cloud provider networks, or geographies outside your partner footprint.
- Bursts of guest account creation events within short time windows on the guest registration endpoint.
Detection Strategies
- Reconcile the list of active guest accounts against the invitation ledger and flag any account with no matching invitation.
- Inspect web server and application logs for POST requests to the guest registration endpoint that lack a valid invitation token parameter.
- Alert on new guest logins immediately followed by access to sensitive chat rooms, file shares, or contact directories.
Monitoring Recommendations
- Forward ChatLuck application and web-tier logs into a centralized analytics platform and retain them for post-incident review.
- Track baseline rates of guest invitations and registrations, and alert on deviations that suggest automated self-registration.
- Review administrative audit trails weekly for guest accounts that appear without an approving inviter.
How to Mitigate CVE-2025-54461
Immediate Actions Required
- Apply the vendor-provided fix documented in the ChatLuck Support Document as soon as it is available for your version.
- Audit existing guest accounts and disable any that cannot be tied to a legitimate invitation.
- Restrict network exposure of the ChatLuck guest registration endpoint to trusted networks or authenticated reverse proxies.
Patch Information
NEOJAPAN has published remediation guidance for multiple security issues affecting ChatLuck. Refer to the ChatLuck Support Document for fixed versions and upgrade instructions, and confirm remediation status via the JVN Security Advisory.
Workarounds
- Place the guest registration endpoint behind a VPN, IP allow-list, or web application firewall rule until the patch is applied.
- Temporarily disable the guest invitation feature if business operations permit, and communicate with external collaborators through alternative channels.
- Require administrator approval for any newly registered guest account before granting access to chat rooms or shared content.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
