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Fedora 43 Coturn Critical IPv4-Mapped Bypass Advisory 2026

Linuxsecurity •LinuxSecurity Advisories • March 5, 2026

The Coturn TURN Server is a VoIP media traffic NAT traversal server and gateway. It can be used as a general-purpose network traffic TURN server/gateway, too. This implementation also includes some extra features. Supported RFCs: TURN specs: - RFC 5766 - base TURN specs - RFC 6062 - TCP relaying TURN extension - RFC 6156 - IPv6 extension for TURN - Experimental DTLS support as client protocol. STUN specs: - RFC 3489 - "classic" STUN - RFC 5389 - base "new" STUN specs - RFC 5769 - test vectors for STUN protocol testing - RFC 5780 - NAT behavior discovery support The implementation fully supports the following client-to-TURN-server protocols: - UDP (per RFC 5766) - TCP (per RFC 5766 and RFC 6062) - TLS (per RFC 5766 and RFC 6062); TLS1.0/TLS1.1/TLS1.2 - DTLS (experimental non-standard feature) Supported relay protocols: - UDP (per RFC 5766) - TCP (per RFC 6062) Supported user databases (for user repository, with passwords or keys, if authentication is required): - SQLite - MySQL - PostgreSQL - Redis Redis can also be used for status and statistics storage and notification. Supported TURN authentication mechanisms: - long-term - TURN REST API (a modification of the long-term mechanism, for time-limited secret-based authentication, for WebRTC applications) The load balancing can be implemented with the following tools (either one or a combination of them): - network load-balancer server - DNS-based load balancing - built-in ALTERNATE-SERVER mechanism. Update Information : Coturn 4.9.0 Multiple security fixes Fix to Web Admin password check Cleanup of deprecated OpenSSL APIs Fix for CVE-2026-27624: Bypass localhost and IP range block using IPv4-mapped IPv6

The Coturn TURN Server is a VoIP media traffic NAT traversal server and gateway.

It can be used as a general-purpose network traffic TURN server/gateway, too.

This implementation also includes some extra features. Supported RFCs:

- RFC 5766 - base TURN specs

- RFC 6062 - TCP relaying TURN extension

- RFC 6156 - IPv6 extension for TURN

- Experimental DTLS support as client protocol.

- RFC 3489 - "classic" STUN

- RFC 5389 - base "new" STUN specs

- RFC 5769 - test vectors for STUN protocol testing

- RFC 5780 - NAT behavior discovery support

The implementation fully supports the following client-to-TURN-server protocols:

- TCP (per RFC 5766 and RFC 6062)

- TLS (per RFC 5766 and RFC 6062); TLS1.0/TLS1.1/TLS1.2

- DTLS (experimental non-standard feature)

Supported relay protocols:

Supported user databases (for user repository, with passwords or keys, if

authentication is required):

Redis can also be used for status and statistics storage and notification.

Supported TURN authentication mechanisms:

- TURN REST API (a modification of the long-term mechanism, for time-limited

secret-based authentication, for WebRTC applications)

The load balancing can be implemented with the following tools (either one or a

combination of them):

- network load-balancer server

- DNS-based load balancing

- built-in ALTERNATE-SERVER mechanism.

Coturn 4.9.0 Multiple security fixes Fix to Web Admin password check Cleanup of deprecated OpenSSL APIs Fix for CVE-2026-27624: Bypass localhost and IP range block using IPv4-mapped IPv6

* Wed Feb 25 2026 Robert Scheck - 4.9.0-1 - Upgrade to 4.9.0 (#2442144) - Add patch to build successfully using OpenSSL 1.1.1 on RHEL 8 * Fri Jan 16 2026 Fedora Release Engineering - 4.8.0-3 - Rebuilt for * Fri Jan 16 2026 Fedora Release Engineering - 4.8.0-2 - Rebuilt for

[ 1 ] Bug #2442550 - CVE-2026-27624 coturn: IPv4-mapped IPv6 bypasses denied-peer-ip ACL

This update can be installed with the "dnf" update program. Use su -c 'dnf upgrade --advisory FEDORA-2026-8cb5571ddc' at the command line. For more information, refer to the dnf documentation available at

The full story

This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.

Fedora Coturn Security Bypass Vulnerabilities Addressed in Recent Updates Fedora has issued critical security advisories for the Coturn TURN Server, addressing significant vulnerabilities that could allow bypass of security measures. Users of Fedora 42 and Fedora 43 are affected by these issues, which include a critical IPv4-mapped bypass and an important security bypass fix. The vulnerabilities are detailed under CVE-2026-27624 and others, necessitating immediate attention from system administrators. 2 sources 75

Extracted Entities

Companies (1)

Fedora

CVEs (1)

CVE-2026-27624