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CVE-2026-53450

Coturn: IPv4-mapped 127.0.0.1 bypasses default loopback peer protection

7.4 HighFix available

Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.13.0, coturn rejects loopback peers by default unless allow-loopback-peers is enabled, but the default loopback guard can be bypassed by using the IPv4-mapped IPv6 peer address ::ffff:127.0.0.1 in a TURN XOR-PEER-ADDRESS attribute. ioa_addr_is_loopback checks for the literal IPv6 loopback shape before IPv4-mapped IPv6 handling, so good_peer_addr does not apply the default loopback rejection and an authenticated TURN client can expose services bound only to localhost on the coturn host through TURN relay traffic. This issue is fixed in version 4.13.0.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
Low

Exploit likelihood

0.29%Unchanged since Jul 11, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.4

Coturn: IPv4-mapped 127.0.0.1 bypasses default loopback peer protection

Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.13.0, coturn rejects loopback peers by default unless allow-loopback-peers is enabled, but the default loopback guard can be bypassed by using the IPv4-mapped IPv6 peer address ::ffff:127.0.0.1 in a TURN XOR-PEER-ADDRESS attribute. ioa_addr_is_loopback checks for the literal IPv6 loopback shape before IPv4-mapped IPv6 handling, so good_peer_addr does not apply the default loopback rejection and an authenticated TURN client can expose services bound only to localhost on the coturn host through TURN relay traffic. This issue is fixed in version 4.13.0.

Record
CVE-2026-53450
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
Weakness
CWE-918
Updated
2026-11-02
EUVDEUVD-2026-42971 7.4

Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.13.0, coturn rejects loopback peers by default unless allow-loopback-peers is enabled, but the default loopback guard can be bypassed by using the IPv4-mapped IPv6 peer address ::ffff:127.0.0.1 in a TURN XOR-PEER-ADDRESS attribute. ioa_addr_is_loopback checks for the literal IPv6 loopback shape before IPv4-mapped IPv6 handling, so good_peer_addr does not apply the default loopback rejection and an authenticated TURN client can expose services bound only to localhost on the coturn host through TURN relay traffic. This issue is fixed in version 4.13.0.

Record
EUVD-2026-42971
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
Updated
2026-11-02
NVD 7.4

Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.13.0, coturn rejects loopback peers by default unless allow-loopback-peers is enabled, but the default loopback guard can be bypassed by using the IPv4-mapped IPv6 peer address ::ffff:127.0.0.1 in a TURN XOR-PEER-ADDRESS attribute. ioa_addr_is_loopback checks for the literal IPv6 loopback shape before IPv4-mapped IPv6 handling, so good_peer_addr does not apply the default loopback rejection and an authenticated TURN client can expose services bound only to localhost on the coturn host through TURN relay traffic. This issue is fixed in version 4.13.0.

Record
CVE-2026-53450
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
Weakness
CWE-918
Updated
2026-11-02
OSV 7.4

Coturn: IPv4-mapped 127.0.0.1 bypasses default loopback peer protection

Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.13.0, coturn rejects loopback peers by default unless allow-loopback-peers is enabled, but the default loopback guard can be bypassed by using the IPv4-mapped IPv6 peer address ::ffff:127.0.0.1 in a TURN XOR-PEER-ADDRESS attribute. ioa_addr_is_loopback checks for the literal IPv6 loopback shape before IPv4-mapped IPv6 handling, so good_peer_addr does not apply the default loopback rejection and an authenticated TURN client can expose services bound only to localhost on the coturn host through TURN relay traffic. This issue is fixed in version 4.13.0.

Record
CVE-2026-53450
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
Weakness
CWE-918
Updated
2026-11-02
OSVDEBIAN-CVE-2026-53450 7.4

Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.13.0, coturn rejects loopback peers by default unless allow-loopback-peers is enabled, but the default loopback guard can be bypassed by using the IPv4-mapped IPv6 peer address ::ffff:127.0.0.1 in a TURN XOR-PEER-ADDRESS attribute. ioa_addr_is_loopback checks for the literal IPv6 loopback shape before IPv4-mapped IPv6 handling, so good_peer_addr does not apply the default loopback rejection and an authenticated TURN client can expose services bound only to localhost on the coturn host through TURN relay traffic. This issue is fixed in version 4.13.0.

Record
DEBIAN-CVE-2026-53450
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
Updated
2026-11-02
OSVUBUNTU-CVE-2026-53450 7.4

Coturn is a free open source implementation of TURN and STUN Server. Prior to 4.13.0, coturn rejects loopback peers by default unless allow-loopback-peers is enabled, but the default loopback guard can be bypassed by using the IPv4-mapped IPv6 peer address ::ffff:127.0.0.1 in a TURN XOR-PEER-ADDRESS attribute. ioa_addr_is_loopback checks for the literal IPv6 loopback shape before IPv4-mapped IPv6 handling, so good_peer_addr does not apply the default loopback rejection and an authenticated TURN client can expose services bound only to localhost on the coturn host through TURN relay traffic. This issue is fixed in version 4.13.0.

Record
UBUNTU-CVE-2026-53450
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
Updated
2026-11-02
OSVopenSUSE-SU-2026:11617-1 No score

coturn-4.17.2-1.1 on GA media

These are all security issues fixed in the coturn-4.17.2-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:11617-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
coturn
Debian:12
 All versions, plus listed versions
4.12.0-14.14.0-14.15.0-14.18.0-14.6.1-14.6.1-2
 None known
coturn
Debian:13
 All versions, plus listed versions
4.12.0-14.14.0-14.15.0-14.18.0-14.6.1-2
 None known
coturn
Debian:14
 before 4.14.0-1, plus listed versions
4.12.0-14.6.1-2
4.14.0-1
coturn
Ubuntu:16.04:LTS
 All versions, plus listed versions
4.4.5.4-24.5.0.2-34.5.0.3-14.5.0.3-1build14.5.0.3-1ubuntu0.24.5.0.3-1ubuntu0.34.5.0.3-1ubuntu0.4
 None known
coturn
Ubuntu:18.04:LTS
 All versions, plus listed versions
4.5.0.6-1ubuntu24.5.0.7-1ubuntu14.5.0.7-1ubuntu24.5.0.7-1ubuntu2.18.04.14.5.0.7-1ubuntu2.18.04.24.5.0.7-1ubuntu2.18.04.3
 None known
coturn
Ubuntu:20.04:LTS
 All versions, plus listed versions
4.5.1.1-1.1build14.5.1.1-1.1build24.5.1.1-1.1ubuntu0.20.04.14.5.1.1-1.1ubuntu0.20.04.2
 None known
coturn
Ubuntu:22.04:LTS
 All versions, plus listed versions
4.5.2-34.5.2-3.1~ubuntu22.04.1
 None known
coturn
Ubuntu:24.04:LTS
 All versions, plus listed versions
4.6.1-1build14.6.1-1build24.6.1-1build34.6.1-1build4
 None known
coturn
Ubuntu:26.10
 All versions, plus listed versions
4.6.1-2build24.12.0-14.14.0-14.15.0-14.18.0-1
 None known
coturn
Ubuntu:26.04:LTS
 All versions, plus listed versions
4.6.1-2build14.6.1-2build2
 None known
coturn
openSUSE:Tumbleweed
From an advisory covering 17 CVEs
 before 4.17.2-1.1
4.17.2-1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-53450 is a high vulnerability (CVSS 7.4) in Coturn, published July 10, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.29%, the 21st percentile. Fixed in coturn 4.14.0-1.

References

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