Coturn
CVE-2026-27624
HIGH
Severity by source
AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Primary rating from GitHub Advisory.
CVSS VectorGitHub Advisory
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Lifecycle Timeline
4DescriptionGitHub Advisory
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.
AnalysisAI
Coturn TURN/STUN server contains an access control bypass that allows remote attackers to reach blocked internal addresses by exploiting IPv4-mapped IPv6 address handling in permission and channel binding requests. The vulnerability bypasses "denied-peer-ip" restrictions designed to block loopback ranges, enabling an attacker to interact with internal services that should be unreachable. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Coturn server configured with 'denied-peer-ip' blocking loopback ranges (127.0.0.0/8) or default loopback restrictions, version prior to 4.9.0. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | CVSS 7.2 (HIGH). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker could exploit this vulnerability to compromise the affected system. |
| Remediation | A vendor patch is available — apply it immediately. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify all Coturn instances in your environment and assess their network exposure and configuration. …
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Vendor StatusVendor
SUSE
Severity: High| Product | Status |
|---|---|
| openSUSE Tumbleweed | Fixed |
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