Coturn
CVE-2026-27624
HIGH
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessSend TURN CreatePermission request
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ExploitSpecify IPv4-mapped IPv6 address ::ffff:127.0.0.1
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ExecutionBypass loopback restrictions
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ImpactAccess internal services
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Access control enforcement
MITRE ATT&CK
1 technique across 1 tactic: Defense Evasion The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | 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. TURN service must be accessible over network (AV:N) with no authentication required (PR:N). |
| Impact | CVSS 7.2 (HIGH). Attack vector: Network. Complexity: Low. Privileges required: None. User interaction: None. Public exploit/POC available. |
| Exploit ScenarioDerived | An attacker could exploit this vulnerability to compromise the affected system. |
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Alert meAnalysisAIv1 – Mar 12, 2026
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.
Earlier versions of this analysis (1)
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. [CVSS 7.2 HIGH]
RemediationAI
A vendor patch is available — apply it immediately. Restrict network access to the affected service where possible.
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
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
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- Exploit and PoC references, threat intelligence from 22 sources
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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
3DescriptionGitHub 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.
Executive ViewAI
A vulnerability in Coturn TURN/STUN server implementations could allow attackers to bypass internal network protections designed to prevent access to loopback and internal IP ranges, potentially exposing backend infrastructure and services. Organizations using Coturn for VoIP, WebRTC, or real-time communication applications face elevated risk of unauthorized internal network reconnaissance and lateral movement attacks.
Apply vendor patch. If immediate patching is not feasible: implement network segmentation to isolate Coturn servers from direct internal network access, enforce strict firewall rules to block internal IP ranges at the perimeter, implement robust logging and monitoring of Coturn traffic for anomalous connection attempts to loopback/internal addresses, and restrict administrative access to Coturn configuration files.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.
Affected Products (CPE)GitHub Advisory
An exploitable heap out-of-bounds read vulnerability exists in the way CoTURN 4.5.1.1 web server parses POST requests. R
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
Remote denial of service in Coturn TURN/STUN server allows unauthenticated attackers to crash ARM64 deployments with a s
In coturn before version 4.5.1.3, there is an issue whereby STUN/TURN response buffer is not initialized properly. Rated
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
Unauthenticated remote attackers can leak residual stack memory from Coturn 4.10.0 by sending a TURN Allocate request wi
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
Same weakness CWE-284 – Improper Access Control
View allSame technique Authentication Bypass
View allVendor StatusVendor
SUSE
Severity: High| Product | Status |
|---|---|
| openSUSE Tumbleweed | Fixed |
Exploit-DB