// For flags

CVE-2020-26262

Loopback bypass in Coturn

Severity Score

7.2
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

1
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

Coturn is free open source implementation of TURN and STUN Server. Coturn before version 4.5.2 by default does not allow peers to connect and relay packets to loopback addresses in the range of `127.x.x.x`. However, it was observed that when sending a `CONNECT` request with the `XOR-PEER-ADDRESS` value of `0.0.0.0`, a successful response was received and subsequently, `CONNECTIONBIND` also received a successful response. Coturn then is able to relay packets to the loopback interface. Additionally, when coturn is listening on IPv6, which is default, the loopback interface can also be reached by making use of either `[::1]` or `[::]` as the peer address. By using the address `0.0.0.0` as the peer address, a malicious user will be able to relay packets to the loopback interface, unless `--denied-peer-ip=0.0.0.0` (or similar) has been specified. Since the default configuration implies that loopback peers are not allowed, coturn administrators may choose to not set the `denied-peer-ip` setting. The issue patched in version 4.5.2. As a workaround the addresses in the address block `0.0.0.0/8`, `[::1]` and `[::]` should be denied by default unless `--allow-loopback-peers` has been specified.

Coturn es una implementación gratuita de código abierto de TURN y STUN Server. Coturn anterior a la versión 4.5.2 por defecto no permite a los peers conectarse y retransmitir paquetes a direcciones loopback en el rango de "127.xxx". Sin embargo, se observó que al enviar una petición "CONNECT" con el valor "XOR-PEER-ADDRESS" de "0.0.0.0", se recibió una respuesta con éxito y, posteriormente, "CONNECTIONBIND" también recibió una respuesta exitosa. Coturn entonces puede retransmitir paquetes hacia la interfaz loopback. Además, cuando coturn está escuchando en IPv6, que es el valor predeterminado, también se puede acceder a la interfaz de bucle invertido haciendo uso de "[::1]" o "[::]" como dirección del mismo nivel. Al usar la dirección "0.0.0.0" como dirección del peer, un usuario malicioso podrá retransmitir paquetes a la interfaz de bucle invertido, a menos que se haya especificado "--denied-peer-ip=0.0.0.0" (o similar). Dado que la configuración predeterminada implica que no se permiten los peers de bucle invertido, los administradores de turno pueden optar por no establecer la configuración "denegado-ip". El problema es parcheado en la versión 4.5.2. Como solución alternativa, las direcciones en el bloque de direcciones "0.0.0.0/8", "[::1]" y "[::]" deben denegarse por defecto a menos que se haya especificado "--allow-loopback-peers".

Coturn version 4.5.1.x suffers from a loopback access control bypass vulnerability.

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None
Attack Vector
Network
Attack Complexity
Low
Authentication
None
Confidentiality
Partial
Integrity
Partial
Availability
None
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2020-10-01 CVE Reserved
  • 2021-01-11 CVE Published
  • 2023-11-08 EPSS Updated
  • 2024-08-04 CVE Updated
  • 2024-08-04 First Exploit
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
CWE
  • CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')
  • CWE-682: Incorrect Calculation
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Coturn Project
Search vendor "Coturn Project"
 Coturn
Search vendor "Coturn Project" for product "Coturn"
 < 4.5.2
Search vendor "Coturn Project" for product "Coturn" and version " < 4.5.2"
-
Affected
Fedoraproject
Search vendor "Fedoraproject"
 Fedora
Search vendor "Fedoraproject" for product "Fedora"
 32
Search vendor "Fedoraproject" for product "Fedora" and version "32"
-
Affected
Fedoraproject
Search vendor "Fedoraproject"
 Fedora
Search vendor "Fedoraproject" for product "Fedora"
 33
Search vendor "Fedoraproject" for product "Fedora" and version "33"
-
Affected