CVE-2021-21394

Denial of service (via resource exhaustion) due to improper input validation on third-party identifier endpoints

Severity Score

6.5

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*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 Mensajería Instantánea y Volp federada abierta. En Synapse anterior a versión 1.28.0 Synapse presenta una falta de comprobación de entrada de algunos parámetros en los endpoints utilizados para confirmar que identificadores de terceros podrían causar un uso excesivo del espacio en disco y la memoria conllevando a un agotamiento de los recursos. Tome en cuenta 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

Low

Authentication

Single

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

References (5)

URL	Tag	Source
https://pypi.org/project/matrix-synapse	Product

URL	Date	SRC

URL	Date	SRC
https://github.com/matrix-org/synapse/pull/9321	2023-11-07
https://github.com/matrix-org/synapse/pull/9393	2023-11-07
https://github.com/matrix-org/synapse/security/advisories/GHSA-w9fg-xffh-p362	2023-11-07

URL	Date	SRC
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY	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"				> 0.17.0 < 1.28.0 Search vendor "Matrix" for product "Synapse" and version " > 0.17.0 < 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