// For flags

CVE-2021-32778

Excessive CPU utilization when closing HTTP/2 streams

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

Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions envoy’s procedure for resetting a HTTP/2 stream has O(N^2) complexity, leading to high CPU utilization when a large number of streams are reset. Deployments are susceptible to Denial of Service when Envoy is configured with high limit on H/2 concurrent streams. An attacker wishing to exploit this vulnerability would require a client opening and closing a large number of H/2 streams. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes to reduce time complexity of resetting HTTP/2 streams. As a workaround users may limit the number of simultaneous HTTP/2 dreams for upstream and downstream peers to a low number, i.e. 100.

Envoy es un proxy L7 de código abierto y un bus de comunicación diseñado para grandes arquitecturas modernas orientadas a servicios. En las versiones afectadas, el procedimiento de Envoy para restablecer un flujo HTTP/2 presenta una complejidad O(N^2), conllevando a un alto uso de la CPU cuando se restablece un gran número de flujos. Los despliegues son susceptibles a una Denegación de Servicio cuando Envoy está configurado con un alto límite de flujos concurrentes H/2. Un atacante que desee explotar esta vulnerabilidad necesitaría un cliente que abriera y cerrara un gran número de flujos H/2. Envoy versiones 1.19.1, 1.18.4, 1.17.4 y 1.16.5, contienen correcciones para reducir la complejidad del tiempo de restablecimiento de los flujos HTTP/2. Como solución, los usuarios pueden limitar el número de sueños HTTP/2 simultáneos para los pares ascendentes y descendentes a un número bajo, es decir, 100.

*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
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
Low
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
  • 2021-05-12 CVE Reserved
  • 2021-08-24 CVE Published
  • 2024-05-09 EPSS Updated
  • 2024-08-03 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-834: Excessive Iteration
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Envoyproxy
Search vendor "Envoyproxy"
 Envoy
Search vendor "Envoyproxy" for product "Envoy"
 >= 1.16.0 < 1.16.5
Search vendor "Envoyproxy" for product "Envoy" and version " >= 1.16.0 < 1.16.5"
-
Affected
Envoyproxy
Search vendor "Envoyproxy"
 Envoy
Search vendor "Envoyproxy" for product "Envoy"
 >= 1.17.0 < 1.17.4
Search vendor "Envoyproxy" for product "Envoy" and version " >= 1.17.0 < 1.17.4"
-
Affected
Envoyproxy
Search vendor "Envoyproxy"
 Envoy
Search vendor "Envoyproxy" for product "Envoy"
 >= 1.18.0 < 1.18.4
Search vendor "Envoyproxy" for product "Envoy" and version " >= 1.18.0 < 1.18.4"
-
Affected
Envoyproxy
Search vendor "Envoyproxy"
 Envoy
Search vendor "Envoyproxy" for product "Envoy"
 1.19.0
Search vendor "Envoyproxy" for product "Envoy" and version "1.19.0"
-
Affected