CVE-2021-21396

Name: CVE-2021-21396
Creator: NVD / NIST
Published: 2021-03-26T22:15:12.947+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.09%

Last modified Jun 17, 2026

CVE-2021-21396 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. 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. EPSS estimates a 1.09% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

6.5/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

EPSS Probability

1.09%

61.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-200

Affected Software

Vendor	Product	Versions
Wire	Wire Server	>= 2021-02-16, < 2021-03-02

References

https://github.com/wireapp/wire-server/commit/7ba2bf4140282557cf215e0b2c354d4d08cd3421Patch, Third Party Advisory
https://github.com/wireapp/wire-server/releases/tag/v2021-03-02Third Party Advisory
https://github.com/wireapp/wire-server/security/advisories/GHSA-qx8q-rhq2-rg4jPatch, Third Party Advisory
https://github.com/wireapp/wire-server/commit/7ba2bf4140282557cf215e0b2c354d4d08cd3421Patch, Third Party Advisory
https://github.com/wireapp/wire-server/releases/tag/v2021-03-02Third Party Advisory
https://github.com/wireapp/wire-server/security/advisories/GHSA-qx8q-rhq2-rg4jPatch, Third Party Advisory

Timeline

Published: Mar 26, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21396?

How severe is CVE-2021-21396?

CVE-2021-21396 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.09% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21396?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-21396?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST