CVE-2021-21382 Detail

Current Description

Restund is an open source NAT traversal server. The restund TURN server can be instructed to open a relay to the loopback address range. This allows you to reach any other service running on localhost which you might consider private. In the configuration that we ship (https://github.com/wireapp/ansible-restund/blob/master/templates/restund.conf.j2#L40-L43) the `status` interface of restund is enabled and is listening on `127.0.0.1`.The `status` interface allows users to issue administrative commands to `restund` like listing open relays or draining connections. It would be possible for an attacker to contact the status interface and issue administrative commands by setting `XOR-PEER-ADDRESS` to `127.0.0.1:{{restund_udp_status_port}}` when opening a TURN channel. We now explicitly disallow relaying to loopback addresses, 'any' addresses, link local addresses, and the broadcast address. As a workaround disable the `status` module in your restund configuration. However there might still be other services running on `127.0.0.0/8` that you do not want to have exposed. The `turn` module can be disabled. Restund will still perform STUN and this might already be enough for initiating calls in your environments. TURN is only used as a last resort when other NAT traversal options do not work. One should also make sure that the TURN server is set up with firewall rules so that it cannot relay to other addresses that you don't want the TURN server to relay to. For example other services in the same VPC where the TURN server is running. Ideally TURN servers should be deployed in an isolated fashion where they can only reach what they need to reach to perform their task of assisting NAT-traversal.


View Analysis Description

Severity



CVSS 3.x Severity and Metrics:

NIST CVSS score
NIST: NVD
Base Score:  9.6 CRITICAL
Vector:  CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

Nist CVSS score does not match with CNA score
CNA:  GitHub, Inc.
Base Score:  8.6 HIGH
Vector:  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N


NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: It is possible that the NVD CVSS may not match that of the CNA. The most common reason for this is that publicly available information does not provide sufficient detail or that information simply was not available at the time the CVSS vector string was assigned.

References to Advisories, Solutions, and Tools

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Hyperlink Resource
https://docs.wire.com/understand/restund.html Vendor Advisory 
https://github.com/coturn/coturn/security/advisories/GHSA-6g6j-r9rf-cm7p Not Applicable 
https://github.com/wireapp/ansible-restund/blob/master/templates/restund.conf.j2#L40-L43 Exploit  Third Party Advisory 
https://github.com/wireapp/restund/pull/7 Exploit  Patch  Third Party Advisory 
https://github.com/wireapp/restund/security/advisories/GHSA-96j5-w9jq-pv2x Exploit  Third Party Advisory 
https://talosintelligence.com/vulnerability_reports/TALOS-2018-0732 Exploit  Third Party Advisory 
https://www.rtcsec.com/post/2021/01/details-about-cve-2020-26262-bypass-of-coturns-default-access-control-protection/#further-concerns-what-else Not Applicable 

Weakness Enumeration

CWE-ID CWE Name Source
CWE-668 Exposure of Resource to Wrong Sphere Provider acceptance level GitHub, Inc.  

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Change History

1 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2021-21382
NVD Published Date:
06/11/2021
NVD Last Modified:
06/29/2021
Source:
GitHub, Inc.