// For flags

CVE-2021-21393

Denial of service (via resource exhaustion) due to improper input validation on groups/communities endpoints

Severity Score

6.5
*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 1.28.0 Synapse is missing input validation of some parameters on the endpoints used to confirm third-party identifiers could cause excessive use of disk space and memory leading to resource exhaustion. Note that the groups feature is not part of the Matrix specification and the chosen maximum lengths are arbitrary. Not all clients might abide by them. Refer to referenced GitHub security advisory for additional details including workarounds.

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 1.28.0. Synapse presenta una falta de comprobación de entrada de algunos parámetros en los endpoints usados para confirmar que los identificadores de terceros podrían causar un uso excesivo del espacio en disco y la memoria conllevando a un agotamiento de los recursos. Note que la funcionalidad de grupos no forma parte de la especificación de Matrix y que las longitudes máximas elegidas son arbitrarias. No todos los clientes pueden acatarlos. Consulte el aviso de seguridad de GitHub al que se hace referencia para obtener detalles adicionales, incluyendo las soluciones

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Attack Vector
Network
Attack Complexity
Medium
Authentication
None
Confidentiality
None
Integrity
None
Availability
Partial
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2020-12-22 CVE Reserved
  • 2021-04-12 CVE Published
  • 2024-08-03 CVE Updated
  • 2024-09-15 EPSS Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-20: Improper Input Validation
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"
> 0.24.0 < 1.28.0
Search vendor "Matrix" for product "Synapse" and version " > 0.24.0 < 1.28.0"
-
Affected
Fedoraproject
Search vendor "Fedoraproject"
Fedora
Search vendor "Fedoraproject" for product "Fedora"
34
Search vendor "Fedoraproject" for product "Fedora" and version "34"
-
Affected