CVE-2026-27624

Coturn is a free open source implementation of TURN and STUN Server. Coturn is commonly configured to block loopback and internal ranges using "denied-peer-ip" and/or default loopback restrictions. CVE-2020-26262 addressed bypasses involving "0.0.0.0", "[::1]" and "[::]", but IPv4-mapped IPv6 is not covered. When sending a "CreatePermission" or "ChannelBind" request with the "XOR-PEER-ADDRESS" value of "::ffff:127.0.0.1", a successful response is received, even though "127.0.0.0/8" is blocked via "denied-peer-ip". The root cause is that, prior to the updated fix implemented in version 4.9.0, three functions in "src/client/ns_turn_ioaddr.c" do not check "IN6_IS_ADDR_V4MAPPED". "ioa_addr_is_loopback()" checks "127.x.x.x" (AF_INET) and "::1" (AF_INET6), but not "::ffff:127.0.0.1." "ioa_addr_is_zero()" checks "0.0.0.0" and "::", but not "::ffff:0.0.0.0." "addr_less_eq()" used by "ioa_addr_in_range()" for "denied-peer-ip" matching: when the range is AF_INET and the peer is AF_INET6, the comparison returns 0 without extracting the embedded IPv4. Version 4.9.0 contains an updated fix to address the bypass of the fix for CVE-2020-26262.

CVSS v3 7.2 HIGH

7.2^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 2.7

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact LOW

Availability Impact NONE

Scope CHANGED

References

Link	Resource
https://github.com/coturn/coturn/commit/b80eb898ba26552600770162c26a8ae7f3661b0b	Patch
https://github.com/coturn/coturn/security/advisories/GHSA-6g6j-r9rf-cm7p	Not Applicable
https://github.com/coturn/coturn/security/advisories/GHSA-j8mm-mpf8-gvjg	Exploit Vendor Advisory
https://github.com/coturn/coturn/security/advisories/GHSA-6g6j-r9rf-cm7p	Not Applicable
https://github.com/coturn/coturn/security/advisories/GHSA-j8mm-mpf8-gvjg	Exploit Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:coturn_project:coturn:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-02-25 05:17

Updated : 2026-02-27 18:04

NVD link : CVE-2026-27624

Mitre link : CVE-2026-27624

CVE.ORG link : CVE-2026-27624

JSON object : View

Products Affected

coturn_project

coturn

CWE

CWE-284

Improper Access Control

CWE-441

Unintended Proxy or Intermediary ('Confused Deputy')

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Coturn is commonly configured to block loopback and internal ranges using \"denied-peer-ip\" and/or default loopback restrictions. CVE-2020-26262 addressed bypasses involving \"0.0.0.0\", \"[::1]\" and \"[::]\", but IPv4-mapped IPv6 is not covered. When sending a \"CreatePermission\" or \"ChannelBind\" request with the \"XOR-PEER-ADDRESS\" value of \"::ffff:127.0.0.1\", a successful response is received, even though \"127.0.0.0/8\" is blocked via \"denied-peer-ip\". The root cause is that, prior to the updated fix implemented in version 4.9.0, three functions in \"src/client/ns_turn_ioaddr.c\" do not check \"IN6_IS_ADDR_V4MAPPED\". \"ioa_addr_is_loopback()\" checks \"127.x.x.x\" (AF_INET) and \"::1\" (AF_INET6), but not \"::ffff:127.0.0.1.\" \"ioa_addr_is_zero()\" checks \"0.0.0.0\" and \"::\", but not \"::ffff:0.0.0.0.\" \"addr_less_eq()\" used by \"ioa_addr_in_range()\" for \"denied-peer-ip\" matching: when the range is AF_INET and the peer is AF_INET6, the comparison returns 0 without extracting the embedded IPv4. Version 4.9.0 contains an updated fix to address the bypass of the fix for CVE-2020-26262."}, {"lang": "es", "value": "Coturn es una implementaci\u00f3n de c\u00f3digo abierto gratuita de servidor TURN y STUN. Coturn se configura com\u00fanmente para bloquear rangos de loopback e internos usando 'denied-peer-ip' y/o restricciones de loopback predeterminadas. CVE-2020-26262 abord\u00f3 evasiones que involucran '0.0.0.0', '[::1]' y '[::]', pero IPv6 mapeado a IPv4 no est\u00e1 cubierto. Al enviar una solicitud 'CreatePermission' o 'ChannelBind' con el valor 'XOR-PEER-ADDRESS' de '::ffff:127.0.0.1', se recibe una respuesta exitosa, aunque '127.0.0.0/8' est\u00e1 bloqueado a trav\u00e9s de 'denied-peer-ip'. La causa ra\u00edz es que, antes de la correcci\u00f3n actualizada implementada en la versi\u00f3n 4.9.0, tres funciones en 'src/client/ns_turn_ioaddr.c' no verifican 'IN6_IS_ADDR_V4MAPPED'. 'ioa_addr_is_loopback()' verifica '127.x.x.x' (AF_INET) y '::1' (AF_INET6), pero no '::ffff:127.0.0.1'. 'ioa_addr_is_zero()' verifica '0.0.0.0' y '::', pero no '::ffff:0.0.0.0'. 'addr_less_eq()' utilizada por 'ioa_addr_in_range()' para la coincidencia de 'denied-peer-ip': cuando el rango es AF_INET y el par es AF_INET6, la comparaci\u00f3n devuelve 0 sin extraer el IPv4 incrustado. La versi\u00f3n 4.9.0 contiene una correcci\u00f3n actualizada para abordar la evasi\u00f3n de la correcci\u00f3n para CVE-2020-26262."}], "lastModified": "2026-02-27T18:04:29.457", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:coturn_project:coturn:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "5C4DE18B-B9AA-4314-B584-7BA316D5D7DB", "versionEndExcluding": "4.9.0"}], "operator": "OR"}]}], "sourceIdentifier": "security-advisories@github.com"}