CVE-2020-26262: Loopback bypass in Coturn
First published: Wed Jan 13 2021(Updated: )
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.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| coturn | <4.5.2 | |
| Red Hat Fedora | =32 | |
| Red Hat Fedora | =33 |
Never miss a vulnerability like this again
Sign up to SecAlerts for real-time vulnerability data matched to your software, aggregated from hundreds of sources.
Reference Links
- https://github.com/coturn/coturn/blob/57180ab60afcaeb13537e69ae8cb8aefd8f3f546/ChangeLog#L48
- https://github.com/coturn/coturn/commit/abfe1fd08d78baa0947d17dac0f7411c3d948e4d
- https://github.com/coturn/coturn/security/advisories/GHSA-6g6j-r9rf-cm7p
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/G54UIUFTEC6RLPOISMB6FUW7456SBZC4/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/M4CJOPAQT43MYAFU3UROGLEXN3Z6RS4H/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/G54UIUFTEC6RLPOISMB6FUW7456SBZC4/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/M4CJOPAQT43MYAFU3UROGLEXN3Z6RS4H/
Frequently Asked Questions
What is the severity of CVE-2020-26262?
CVE-2020-26262 is classified as a medium severity vulnerability.
How do I fix CVE-2020-26262?
To fix CVE-2020-26262, upgrade Coturn to version 4.5.2 or later.
Which software versions are affected by CVE-2020-26262?
CVE-2020-26262 affects Coturn versions prior to 4.5.2 as well as Fedora 32 and 33.
What type of vulnerability is CVE-2020-26262?
CVE-2020-26262 is a vulnerability that allows unauthorized connections to loopback addresses.
Can CVE-2020-26262 be exploited by external attackers?
Yes, CVE-2020-26262 can be exploited by attackers who can send crafted CONNECT requests.
- agent/weakness
- agent/type
- collector/mitre-cve
- source/MITRE
- agent/last-modified-date
- agent/title
- agent/severity
- agent/author
- agent/remedy
- agent/references
- agent/description
- agent/first-publish-date
- agent/event
- agent/source
- agent/softwarecombine
- agent/tags
- collector/nvd-index
- agent/software-canonical-lookup-request
- vendor/coturn project
- canonical/coturn
- vendor/fedoraproject
- canonical/red hat fedora
- version/red hat fedora/32
- version/red hat fedora/33