CVE-2020-26262
Loopback bypass in Coturn
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
7.2
Loopback bypass in Coturn
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.
- Record
CVE-2020-26262- CVSS 3.1
- 7.2 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N - Weakness
- CWE-441, CWE-682
- Updated
- 2026-11-02
EUVDEUVD-2020-18850
7.2
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.
- Record
EUVD-2020-18850- CVSS 3.1
- 7.2 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N - Updated
- 2026-11-03
NVD
7.2
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.
- Record
CVE-2020-26262- CVSS 3.1
- 7.2 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N - CVSS 2.0
- 6.4 Medium
AV:N/AC:L/Au:N/C:P/I:P/A:N - Weakness
- CWE-441, CWE-682
- Updated
- 2026-11-02
OSVALPINE-CVE-2020-26262
7.2
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.
- Record
ALPINE-CVE-2020-26262- CVSS 3.1
- 7.2 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N - Updated
- 2026-11-03
OSV
7.2
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.
- Record
CVE-2020-26262- CVSS 3.1
- 7.2 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVDEBIAN-CVE-2020-26262
7.2
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.
- Record
DEBIAN-CVE-2020-26262- CVSS 3.1
- 7.2 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
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OSVUBUNTU-CVE-2020-26262
7.2
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.
- Record
UBUNTU-CVE-2020-26262- CVSS 3.1
- 7.2 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVMGASA-2021-0087 No score
Updated coturn package fixes a security vulnerability
When sending a CONNECT request with the XOR-PEER-ADDRESS value of 0.0.0.0, a malicious user would be 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 (CVE-2020-26262).
If updating is not possible, the setting --denied-peer-ip=0.0.0.0 can mitigate this issue.
The coturn package has been patched to fix this issue.
- Record
MGASA-2021-0087- Updated
- 2026-11-02
OSVopenSUSE-SU-2024:10696-1 No score
coturn-4.5.2-2.2 on GA media
These are all security issues fixed in the coturn-4.5.2-2.2 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2024:10696-1- Updated
- 2026-11-02
OSVUSN-4690-1 No score
coturn vulnerability
It was discovered that coTURN allowed peers to connect and relay packets to loopback addresses in the range of 127.x.x.x. A malicious user could use this vulnerability to insert packages into the loopback interface.
- Record
USN-4690-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
coturnAlpine:v3.13 |
before 4.5.2-r0 | 4.5.2-r0 |
coturnAlpine:v3.14 |
before 4.5.2-r0 | 4.5.2-r0 |
coturnAlpine:v3.15 |
before 4.5.2-r0 | 4.5.2-r0 |
coturnAlpine:v3.16 |
before 4.5.2-r0 | 4.5.2-r0 |
coturnAlpine:v3.17 |
before 4.5.2-r0 | 4.5.2-r0 |
coturnAlpine:v3.18 |
before 4.5.2-r0 | 4.5.2-r0 |
coturnAlpine:v3.19 |
before 4.5.2-r0 | 4.5.2-r0 |
coturnAlpine:v3.20 |
before 4.5.2-r0 | 4.5.2-r0 |
coturnAlpine:v3.21 |
before 4.5.2-r0 | 4.5.2-r0 |
coturnAlpine:v3.22 |
before 4.5.2-r0 | 4.5.2-r0 |
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| Package | Affected | Fixed |
|---|---|---|
coturnAlpine:v3.23 |
before 4.5.2-r0 | 4.5.2-r0 |
coturnAlpine:v3.24 |
before 4.5.2-r0 | 4.5.2-r0 |
coturnDebian:12 |
before 4.5.2-1 | 4.5.2-1 |
coturnDebian:13 |
before 4.5.2-1 | 4.5.2-1 |
coturnDebian:14 |
before 4.5.2-1 | 4.5.2-1 |
coturnDebian:9 |
before 4.5.0.5-1+deb9u3, plus listed versions 4.5.0.5-14.5.0.5-1+deb9u14.5.0.5-1+deb9u2 |
4.5.0.5-1+deb9u3 |
coturnDebian:10 |
before 4.5.1.1-1.1+deb10u2, plus listed versions 4.5.1.1-1.14.5.1.1-1.1+deb10u1 |
4.5.1.1-1.1+deb10u2 |
coturnMageia:7 |
before 4.5.2-1.4.mga7 | 4.5.2-1.4.mga7 |
coturnUbuntu:16.04:LTS |
before 4.5.0.3-1ubuntu0.4, plus listed versions 4.4.5.4-24.5.0.2-34.5.0.3-14.5.0.3-1build14.5.0.3-1ubuntu0.24.5.0.3-1ubuntu0.3 |
4.5.0.3-1ubuntu0.4 |
coturnUbuntu:18.04:LTS |
before 4.5.0.7-1ubuntu2.18.04.3, plus listed versions 4.5.0.6-1ubuntu24.5.0.7-1ubuntu14.5.0.7-1ubuntu24.5.0.7-1ubuntu2.18.04.14.5.0.7-1ubuntu2.18.04.2 |
4.5.0.7-1ubuntu2.18.04.3 |
coturnUbuntu:20.04:LTS |
before 4.5.1.1-1.1ubuntu0.20.04.2, plus listed versions 4.5.1.1-1.1build14.5.1.1-1.1build24.5.1.1-1.1ubuntu0.20.04.1 |
4.5.1.1-1.1ubuntu0.20.04.2 |
coturnopenSUSE:Tumbleweed From an advisory covering 3 CVEs |
before 4.5.2-2.2 | 4.5.2-2.2 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| affected, aliases, references | OSV | |
| aliases | EUVD | |
| first indexed | CVE List, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-26262 is a high vulnerability (CVSS 7.2) in Coturn, published January 11, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.55%, the 75th percentile. Fixed in coturn 4.5.2-r0.
References
github.com/coturn/coturn/security/advisories/GHSA-6g6j-r9rf-cm7p
github.com/coturn/coturn/commit/abfe1fd08d78baa0947d17dac0f7411c3d948e4d
github.com/coturn/coturn/blob/57180ab60afcaeb13537e69ae8cb8aefd8f3f546/ChangeLog
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/G54UIUFTEC6RLPOISMB6FUW7456SBZC4
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/M4CJOPAQT43MYAFU3UROGLEXN3Z6RS4H
security.alpinelinux.org/vuln/CVE-2020-26262
Show 9 moreShow less
security-tracker.debian.org/tracker/CVE-2020-26262
advisories.mageia.org/MGASA-2021-0087.html
bugs.mageia.org/show_bug.cgi?id=28068
ubuntu.com/security/CVE-2020-26262
ubuntu.com/security/notices/USN-4690-1
cve.org/CVERecord?id=CVE-2020-26262
suse.com/security/cve/CVE-2020-26262
suse.com/security/cve/CVE-2020-4067
suse.com/security/cve/CVE-2020-6061