CVE-2026-27624Public exploitNetwork attack vector

Denied-peer access via IPv4-mapped IPv6 ACL bypass

Published Feb 25, 2026 · Updated Feb 25, 2026

Access-control bypass in coturn before 4.9.0 allows remote attackers to reach denied IPv4 peers through IPv4-mapped IPv6 addresses. In src/client/ns_turn_ioaddr.c, ioa_addr_is_loopback, ioa_addr_is_zero, and ioa_addr_in_range fail to normalize mapped addresses before IPv4 checks. A crafted XOR-PEER-ADDRESS therefore passes denied-peer-ip; relay reachability depends on IPv6 enablement, socket binding, and host OS routing.

CVSS severity7.2
High
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Access-control bypass in coturn before 4.9.0 allows remote attackers to reach denied IPv4 peers through IPv4-mapped IPv6 addresses. In src/client/ns_turn_ioaddr.c, ioa_addr_is_loopback, ioa_addr_is_zero, and ioa_addr_in_range fail to normalize mapped addresses before IPv4 checks. A crafted XOR-PEER-ADDRESS therefore passes denied-peer-ip; relay reachability depends on IPv6 enablement, socket binding, and host OS routing.

The record

CVE
CVE-2026-27624
Published
Feb 25, 2026
Updated
Feb 25, 2026
Vendor
coturn
Product
coturn
Classifications
CWE-284, CWE-441, T1090
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

coturn · coturnversion=< 4.9.0

Published CVSS scores

7.2GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-284Improper Access Control
CWE-441Unintended Proxy or Intermediary ('Confused Deputy')
T1090Proxy

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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