CVE-2026-27624 (GCVE-0-2026-27624)

Vulnerability from cvelistv5 – Published: 2026-02-25 04:04 – Updated: 2026-02-25 15:09
VLAI
Title
Coturn: IPv4-mapped IPv6 (::ffff:0:0/96) bypasses denied-peer-ip ACL
Summary
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.
Severity
7.2 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
SSVC
Exploitation: poc Automatable: yes Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-284 - Improper Access Control
  • CWE-441 - Unintended Proxy or Intermediary ('Confused Deputy')
Assigner
References
Impacted products
Vendor Product Version
coturn coturn Affected: < 4.9.0
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CVE-2020-26262 abord\u00f3 evasiones que involucran \u00270.0.0.0\u0027, \u0027[::1]\u0027 y \u0027[::]\u0027, pero IPv6 mapeado a IPv4 no est\u00e1 cubierto. Al enviar una solicitud \u0027CreatePermission\u0027 o \u0027ChannelBind\u0027 con el valor \u0027XOR-PEER-ADDRESS\u0027 de \u0027::ffff:127.0.0.1\u0027, se recibe una respuesta exitosa, aunque \u0027127.0.0.0/8\u0027 est\u00e1 bloqueado a trav\u00e9s de \u0027denied-peer-ip\u0027. La causa ra\u00edz es que, antes de la correcci\u00f3n actualizada implementada en la versi\u00f3n 4.9.0, tres funciones en \u0027src/client/ns_turn_ioaddr.c\u0027 no verifican \u0027IN6_IS_ADDR_V4MAPPED\u0027. \u0027ioa_addr_is_loopback()\u0027 verifica \u0027127.x.x.x\u0027 (AF_INET) y \u0027::1\u0027 (AF_INET6), pero no \u0027::ffff:127.0.0.1\u0027. \u0027ioa_addr_is_zero()\u0027 verifica \u00270.0.0.0\u0027 y \u0027::\u0027, pero no \u0027::ffff:0.0.0.0\u0027. \u0027addr_less_eq()\u0027 utilizada por \u0027ioa_addr_in_range()\u0027 para la coincidencia de \u0027denied-peer-ip\u0027: cuando el rango es AF_INET y el par es AF_INET6, la comparaci\u00f3n devuelve 0 sin extraer el IPv4 incrustado. 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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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