// For flags

CVE-2021-29430

Denial of service attack via memory exhaustion

Severity Score

7.5
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

Sydent is a reference Matrix identity server. Sydent does not limit the size of requests it receives from HTTP clients. A malicious user could send an HTTP request with a very large body, leading to memory exhaustion and denial of service. Sydent also does not limit response size for requests it makes to remote Matrix homeservers. A malicious homeserver could return a very large response, again leading to memory exhaustion and denial of service. This affects any server which accepts registration requests from untrusted clients. This issue has been patched by releases 89071a1, 0523511, f56eee3. As a workaround request sizes can be limited in an HTTP reverse-proxy. There are no known workarounds for the problem with overlarge responses.

Sydent es un servidor de identidad Matrix de referencia. Sydent no limita el tamaño de las peticiones que recibe de los clientes HTTP. Un usuario malicioso podría enviar una petición HTTP con un cuerpo muy grande, conllevando al agotamiento de la memoria y una denegación de servicio. Sydent tampoco limita el tamaño de respuesta para las peticiones que realiza a los servidores domésticos de Matrix remotos. Un servidor doméstico malicioso podría devolver una respuesta muy grande, lo que nuevamente conlleva al agotamiento de la memoria y a una denegación de servicio. Esto afecta a cualquier servidor que acepte peticiones de registro de clientes no confiables. Este problema ha sido parcheado para las versiones 89071a1, 0523511, f56eee3. Como solución alternativa, los tamaños de las peticiones pueden ser limitados en un proxy inverso HTTP. No se conocen soluciones alternativas para el problema de las respuestas demasiado grandes

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Attack Vector
Network
Attack Complexity
Low
Authentication
None
Confidentiality
None
Integrity
None
Availability
Partial
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2021-03-30 CVE Reserved
  • 2021-04-15 CVE Published
  • 2023-12-30 EPSS Updated
  • 2024-08-03 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-20: Improper Input Validation
  • CWE-400: Uncontrolled Resource Consumption
  • CWE-770: Allocation of Resources Without Limits or Throttling
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"
Sydent
Search vendor "Matrix" for product "Sydent"
< 2.3.0
Search vendor "Matrix" for product "Sydent" and version " < 2.3.0"
-
Affected