Coturn: IPv4-mapped 127.0.0.1 bypasses default loopback peer protection

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Summary

CVECVE-2026-53450
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-10 19:17:24 UTC
Updated2026-07-10 20:16:46 UTC
DescriptionCoturn 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.

Risk And Classification

Primary CVSS: v3.1 7.4 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L

EPSS: 0.002870000 probability, percentile 0.205690000 (date 2026-07-12)

Problem Types: CWE-918 | CWE-918 CWE-918: Server-Side Request Forgery (SSRF)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.4HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
3.1CNADECLARED7.4HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Coturn Coturn affected < 4.13.0 Not specified

References

ReferenceSourceLinkTags
github.com/coturn/coturn/security/advisories/GHSA-w4hf-cr3w-6h79 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/coturn/coturn/commit/b057acbebe721c8f2f202ddad5e16289e295c754 [email protected] github.com
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