Improper Access Control Affecting coturn package, versions <4.10.0-r0


Severity

Recommended
0.0
medium
0
10

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Threat Intelligence

EPSS
0.05% (17th percentile)

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  • Snyk IDSNYK-ALPINE323-COTURN-16344695
  • published2 May 2026
  • disclosed25 Feb 2026

Introduced: 25 Feb 2026

CVE-2026-27624  (opens in a new tab)
CWE-284  (opens in a new tab)
CWE-441  (opens in a new tab)

How to fix?

Upgrade Alpine:3.23 coturn to version 4.10.0-r0 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream coturn package and not the coturn package as distributed by Alpine. See How to fix? for Alpine:3.23 relevant fixed versions and status.

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 Base Scores

version 3.1