External risk intelligence

OpenClaw Nextcloud Talk Allowlist Bypass via Display Name Spoofing

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2026-28474

The vulnerability affects a Nextcloud Talk plugin, which is a communication and collaboration tool commonly deployed as an internet-facing web application or service to facilitate remote conversations, making the vulnerable functionality frequently accessible via the public internet.

Openclaw

before 2026.2.6

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This vulnerability involves a plugin for Nextcloud Talk that allows unauthorized access to private conversations by bypassing allowlist protections. The issue stems from how the plugin validates user display names, enabling an attacker to impersonate an allowed user to gain entry. The main concern is confirming relevance and exposure, as this could impact the confidentiality of communications within your organization if the affected plugin is in use.

Allows unauthorized access to private chats.
Important for protecting confidential conversations.
Verify if your Talk plugin is affected.

Attack Path

How an attacker could exploit the issue

An attacker can bypass access restrictions in Nextcloud Talk by manipulating their display name to impersonate an authorized user. This allows them to access private messages and restricted rooms that they would otherwise be prevented from joining.

No specific entry conditions are required.
Display name spoofing triggers the vulnerability.
Unauthorized access to private conversations.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an attacker to bypass restrictions in direct message and room allowlists within the Nextcloud Talk plugin. By changing their Nextcloud display name to mimic an allowlisted user ID, an attacker may gain unauthorized access to private conversations when supported by the advisory's conditions.

Private conversations and user data.
Display name spoofing.
Unauthorized access to discussions.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in the OpenClaw Nextcloud Talk plugin, which allows unauthorized access to conversations by spoofing display names, likely falls under the responsibility of the platform or infrastructure team managing the Nextcloud instance. The first practical step is to identify all Nextcloud instances, determine which are running the affected Talk plugin, and assess their exposure and business criticality. Then, engage the application owner to plan remediation.

Platform/Infrastructure team owns remediation.
Verify Nextcloud Talk plugin and reachability.
Plan upgrade during next maintenance window.

Supplementary metadata

CVSS vector

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Frequently asked questions

What is the OpenClaw Nextcloud Talk plugin?

OpenClaw provides a plugin for Nextcloud Talk, a collaborative platform used by organizations to host private messaging, group chats, and real-time audio or video conferencing. This plugin specifically manages access controls for these communication channels, ensuring that only permitted participants can join private discussions or sensitive rooms.

What is the vulnerability in CVE-2026-28474?

This vulnerability is classified as CWE-863, which concerns improper authorization. The plugin incorrectly relies on the mutable 'display name' field—a string that users can typically change—to verify identity against an allowlist. Because the system checks this name rather than a permanent, immutable user ID, an attacker can simply rename their account to match an authorized user to bypass security checks.

How does an attacker trigger this bypass?

An attacker triggers this flaw by changing their account's display name to match a value already present on the room or direct message allowlist. No complex exploit or specific system state is required; if the plugin is configured to check display names for permissions, it will grant access to the attacker as if they were the legitimate user. Simply accessing a public-facing conversation does not trigger the bug; it requires the interaction with restricted or allowlisted content.

Is my organization at risk for CVE-2026-28474?

Halo Surface Signal indicates that because this plugin facilitates communication, it is often deployed as an internet-facing service. If you use this plugin on a Nextcloud instance accessible from the public internet, the risk is higher as unauthorized remote parties could potentially spoof identities. Internal-only instances still face risk from authenticated users who could spoof other internal identities to gain unauthorized access.

What should I do to address this vulnerability?

First, inventory your organization's Nextcloud installations to identify where the OpenClaw Talk plugin is currently active. Once identified, check the installed version; if it is older than 2026.2.6, plan to update to a patched version as soon as possible. Coordinate with the teams managing your Nextcloud infrastructure to schedule this maintenance and ensure access control logic is properly updated.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.