CVE-2021-21396

Bulk list client endpoint exposes too much metadata about a client

MEDIUM
6.5
CVSS Score
Published: March 26, 2021 at 09:40 PM UTC
Updated: June 17, 2026 at 03:35 AM UTC
2 products affected across 2 vendorsWire ServerWire Server

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Severity
MEDIUM6.5
Exploit prediction
EPSS 1%

Description

wire-server is an open-source back end for Wire, a secure collaboration platform. In wire-server from version 2021-02-16 and before version 2021-03-02, the client metadata of all users was exposed in the `GET /users/list-clients` endpoint. The endpoint could be used by any logged in user who could request client details of any other user (no connection required) as far as they can find their User ID. The exposed metadata included id, class, type, location, time, and cookie. A user on a Wire backend could use this endpoint to find registration time and location for each device for a given list of users. As a workaround, remove `/list-clients` from nginx config. This has been fixed in version 2021-03-02.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

2021-02-16 ≤ v < 2021-03-02
Affected range stops below 2021-03-02, so it looks safe — our inference, not a vendor statement
v < 2021-3-2
Affected range stops below 2021-3-2, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

6.5MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-200

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