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Vulnerability · Published Jan 13, 2021 · Assigned by GitHub_M

CVE-2020-26262Loopback bypass in Coturn

High 7.2

In plain English

A high-severity security flaw in coturn from coturn. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.5% (higher than 75% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.2High
Exploit odds (30 days)1.5%top 24.9% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.20coturn4.5.2-r0ALPINE-CVE-2020-26262
Alpine:v3.21coturn4.5.2-r0ALPINE-CVE-2020-26262
Alpine:v3.22coturn4.5.2-r0ALPINE-CVE-2020-26262
Alpine:v3.23coturn4.5.2-r0ALPINE-CVE-2020-26262
Alpine:v3.24coturn4.5.2-r0ALPINE-CVE-2020-26262
Debian:12coturn4.5.2-1DEBIAN-CVE-2020-26262
Debian:13coturn4.5.2-1DEBIAN-CVE-2020-26262
Debian:14coturn4.5.2-1DEBIAN-CVE-2020-26262

Affected products (as reported)

VendorProductVersions
coturn coturn < 4.5.2

Weakness: CWE-441, CWE-682 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

References