// For flags

CVE-2021-21273

Open redirects on some federation and push requests

Severity Score

6.1
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.25.0, requests to user provided domains were not restricted to external IP addresses when calculating the key validity for third-party invite events and sending push notifications. This could cause Synapse to make requests to internal infrastructure. The type of request was not controlled by the user, although limited modification of request bodies was possible. For the most thorough protection server administrators should remove the deprecated `federation_ip_range_blacklist` from their settings after upgrading to Synapse v1.25.0 which will result in Synapse using the improved default IP address restrictions. See the new `ip_range_blacklist` and `ip_range_whitelist` settings if more specific control is necessary.

Synapse es un servidor doméstico de referencia de Matrix escrito en python (paquete pypi matrix-synapse). Matrix es un ecosistema para VoIP y mensajería instantánea federada abierta. En Synapse versiones anteriores a 1.25.0, las peticiones a los dominios proporcionados por el usuario no estaban restringidas para direcciones IP externas al calcular la validez de la clave para eventos de invitación de terceros y enviar notificaciones automáticas. Esto podría causar que Synapse realice peticiones a la infraestructura interna. El tipo de petición no era controlada por el usuario, aunque una modificación limitada de los cuerpos de petición era posible. Para obtener la protección más completa, los administradores del servidor deben eliminar la obsoleta "federation_ip_range_blacklist" de su configuración después de actualizar a Synapse versión v1.25.0, lo que resultará en que Synapse use las restricciones de dirección IP predeterminadas mejoradas. Consulte la nueva configuración de "ip_range_blacklist" e "ip_range_whitelist" si es necesario un control más específico

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None
Attack Vector
Network
Attack Complexity
Medium
Authentication
None
Confidentiality
Partial
Integrity
Partial
Availability
None
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2020-12-22 CVE Reserved
  • 2021-02-26 CVE Published
  • 2023-11-12 EPSS Updated
  • 2024-08-03 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
CAPEC
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"
 < 1.25.0
Search vendor "Matrix" for product "Synapse" and version " < 1.25.0"
-
Affected
Fedoraproject
Search vendor "Fedoraproject"
 Fedora
Search vendor "Fedoraproject" for product "Fedora"
 34
Search vendor "Fedoraproject" for product "Fedora" and version "34"
-
Affected