CVE-2021-39163

Adding a private/unlisted room to a community exposes room metadata in an unauthorised manner.

Severity Score

3.1

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

*SSVC

Descriptions

Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted. Server administrators should upgrade to 1.41.1 or higher to patch the vulnerability. There are two potential workarounds. Server administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators. Administrators that are using a reverse proxy could, with partial loss of group functionality, block the endpoints `/_matrix/client/r0/groups/{group_id}/rooms` and `/_matrix/client/unstable/groups/{group_id}/rooms`.

Matrix es un ecosistema para la Mensajería Instantánea federada abierta y Voz sobre IP. En versiones 1.41.0 y anteriores, unos usuarios no autorizados pueden acceder al nombre, avatar, tema y número de miembros de una sala si conocen el ID de la misma. Esta vulnerabilidad es limitada a servidores domésticos en los que el servidor doméstico vulnerable se encuentra en la sala y los usuarios no confiables pueden crear grupos (comunidades). Por defecto, sólo los administradores de servidores domésticos pueden crear grupos. Sin embargo, los administradores de homeservers ya pueden acceder a esta información en la base de datos o usando la API de administración. Como resultado, sólo los servidores domésticos en los que el ajuste de configuración "enable_group_creation" es ajustado en "true" están afectados. Los administradores de servidores deben actualizar a versión 1.41.1 o superior para parchear la vulnerabilidad. Se presenta dos posibles soluciones. Los administradores del servidor pueden ajustar "enable_group_creation" en 'false" en la configuración de su servidor doméstico (este es el valor por defecto) para prevenir la creación de grupos por parte de no administradores. Los administradores que están usando un proxy inverso podrían, con pérdida parcial de la funcionalidad group, bloquear los endpoints "/_matrix/client/r0/groups/{group_id}/rooms" y "/_matrix/client/unstable/groups/{group_id}/rooms"

*Credits: N/A

Attack Vector

Network

Attack Complexity

High

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Attack Vector

Network

Attack Complexity

Medium

Authentication

Single

Confidentiality

Partial

Integrity

None

Availability

None

* Common Vulnerability Scoring System

SSVC

Decision:-

Exploitation

Automatable

Tech. Impact

* Organization's Worst-case Scenario

Timeline

2021-08-16 CVE Reserved
2021-08-31 CVE Published
2023-11-08 EPSS Updated
2024-08-04 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
CWE-863: Incorrect Authorization

CAPEC

References (5)

URL	Tag	Source
https://github.com/matrix-org/synapse/releases/tag/v1.41.1	Release Notes
https://github.com/matrix-org/synapse/security/advisories/GHSA-jj53-8fmw-f2w2	Mitigation

URL	Date	SRC

URL	Date	SRC
https://github.com/matrix-org/synapse/commit/cb35df940a	2023-11-07

URL	Date	SRC
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2VHDEPCZ22GJFMZCWA2XZAGPOEV72POF	2023-11-07
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PXT7ID7DNBRN2TVTETU3SYQHJKEG6PXN	2023-11-07

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Matrix Search vendor "Matrix"		Synapse Search vendor "Matrix" for product "Synapse"				< 1.41.1 Search vendor "Matrix" for product "Synapse" and version " < 1.41.1"		-		Affected
Fedoraproject Search vendor "Fedoraproject"		Fedora Search vendor "Fedoraproject" for product "Fedora"				34 Search vendor "Fedoraproject" for product "Fedora" and version "34"		-		Affected
Fedoraproject Search vendor "Fedoraproject"		Fedora Search vendor "Fedoraproject" for product "Fedora"				35 Search vendor "Fedoraproject" for product "Fedora" and version "35"		-		Affected