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
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. Public exploit code exists for this flaw, and a patch is available in version 4.9.0 and later.
Technical ContextAI
Classified as CWE-284 (Improper Access Control). Affects Coturn. 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 vi
RemediationAI
A vendor patch is available — apply it immediately. Restrict network access to the affected service where possible.
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An exploitable denial-of-service vulnerability exists in the way CoTURN 4.5.1.1 web server parses POST requests. Rated h
Stack buffer overflow in Coturn's OAuth token decoder (decode_oauth_token_gcm()) lets remote unauthenticated attackers c
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Server-side request forgery in coturn TURN/STUN server before 4.13.0 lets an authenticated TURN client bypass the defaul
SQL injection in the Coturn TURN/STUN server's HTTPS admin panel (versions prior to 4.12.0) allows an authenticated admi
Format string injection in Coturn prior to 4.13.0 lets an authenticated TURN user crash the relay server or leak stack m
Memory exhaustion in Coturn 4.15.0 allows an authenticated TURN user to crash or degrade server availability by abusing
Arbitrary file overwrite in Coturn prior to 4.13.0 is possible through the CLI management interface's `psd` (print sessi
Stored XSS in Coturn's web-admin HTTPS interface (all versions prior to 4.11.0) allows a TURN-level attacker to inject p
TCP/TLS stream parser desynchronization in Coturn TURN/STUN server prior to 4.15.0 allows any unauthenticated remote cli
Same weakness CWE-284 – Improper Access Control
View allSame technique Authentication Bypass
View allVendor StatusVendor
SUSE
Severity: High| Product | Status |
|---|---|
| openSUSE Tumbleweed | Fixed |
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