// For flags

CVE-2021-21299

Multiple Transfer-Encoding headers misinterprets request payload

Severity Score

8.1
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

hyper is an open-source HTTP library for Rust (crates.io). In hyper from version 0.12.0 and before versions 0.13.10 and 0.14.3 there is a vulnerability that can enable a request smuggling attack. The HTTP server code had a flaw that incorrectly understands some requests with multiple transfer-encoding headers to have a chunked payload, when it should have been rejected as illegal. This combined with an upstream HTTP proxy that understands the request payload boundary differently can result in "request smuggling" or "desync attacks". To determine if vulnerable, all these things must be true: 1) Using hyper as an HTTP server (the client is not affected), 2) Using HTTP/1.1 (HTTP/2 does not use transfer-encoding), 3) Using a vulnerable HTTP proxy upstream to hyper. If an upstream proxy correctly rejects the illegal transfer-encoding headers, the desync attack cannot succeed. If there is no proxy upstream of hyper, hyper cannot start the desync attack, as the client will repair the headers before forwarding. This is fixed in versions 0.14.3 and 0.13.10. As a workaround one can take the following options: 1) Reject requests that contain a `transfer-encoding` header, 2) Ensure any upstream proxy handles `transfer-encoding` correctly.

hyper es una biblioteca HTTP de código abierto para Rust (crates.io). En Hyper desde la versión 0.12.0 y antes de las versiones 0.13.10 y 0.14.3, se presenta una vulnerabilidad que puede habilitar un ataque de trafico no autorizado de peticiones. El código del servidor HTTP tenía un fallo que entiende incorrectamente que algunas peticiones con múltiples encabezados transfer-encoding tienen una carga útil fragmentada, cuando debería haber sido rechazada como ilegal. Esto, combinado con un proxy HTTP aguas arriba que entiende el límite de carga útil de la petición de manera diferente, puede resultar en "request smuggling" o "desync attacks". Para determinar si es vulnerable, todas estas cosas deben ser ciertas: 1) Usar Hyper como servidor HTTP (el cliente no se ve afectado), 2) Usar HTTP/1.1 (HTTP/2 no usa transfer-encoding), 3) Usar un Proxy HTTP vulnerable aguas arriba de hiper. Si un proxy aguas arriba rechaza correctamente los encabezados transfer-encoding ilegales, el ataque de desincronización no puede tener éxito. Si no existe un proxy aguas arriba de Hyper, Hyper no puede iniciar el ataque de desincronización, ya que el cliente reparará los encabezados antes de reenviar. Esto se corrige en las versiones 0.14.3 y 0.13.10. Como solución alternativa, se pueden tomar las siguientes opciones: 1) Rechazar las peticiones que contengan un encabezado "transfer-encoding", 2) Asegurarse de que cualquier proxy ascendente maneje correctamente "transfer-encoding"

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None
Attack Vector
Network
Attack Complexity
Medium
Authentication
None
Confidentiality
Partial
Integrity
Partial
Availability
Partial
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2020-12-22 CVE Reserved
  • 2021-02-11 CVE Published
  • 2023-10-28 EPSS Updated
  • 2024-08-03 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Hyper
Search vendor "Hyper"
Hyper
Search vendor "Hyper" for product "Hyper"
>= 0.12.0 < 0.13.10
Search vendor "Hyper" for product "Hyper" and version " >= 0.12.0 < 0.13.10"
rust
Affected
Hyper
Search vendor "Hyper"
Hyper
Search vendor "Hyper" for product "Hyper"
>= 0.14.0 < 0.14.3
Search vendor "Hyper" for product "Hyper" and version " >= 0.14.0 < 0.14.3"
rust
Affected