Coturn 4.17.2

What's Changed

• Fix outgoing UDP TTL pinned to 1 on client-facing sockets

Coturn 4.17.1

• Gate merges on the more tests suites
• build: Drop ginstall detection in configure
• Flash before socket close

Coturn 4.17.0

Upgrade notes

Three defaults changed in this release. Read these before upgrading.

DTLS listeners are now opt-in. The server no longer starts DTLS listeners unless --dtls is given. A deployment that relied on DTLS being up by default will stop serving DTLS clients after the upgrade, without an error. The deprecated --no-dtls / --no-dtls=false spellings are still accepted and now warn.

Stateless nonce is on by default. Challenge nonces are authenticated timestamp cookies rather than a random value stored per session, so unauthenticated UDP requests are answered from the listener without allocating a session. Two consequences:

• The challenge NONCE is now 24 characters instead of 16. RFC 8489 requires clients to treat it as an opaque string of up to 128 characters, so compliant clients are unaffected. --stateless-nonce=false restores the previous behaviour.
• The signing key is generated per process, so a restart costs each client one 438 re-authentication round-trip, as does a retry that lands on a different instance behind a load balancer. Set --stateless-nonce-secret to the same value across a fleet to avoid both.

The default log line changed. Timestamps are ISO-8601 with millisecond precision, the thread id is gone, the field delimiter is a single space instead of :, and each record now occupies exactly one line. Log shippers and any downstream parsing will need updating; the default line is now:

2026-08-02T17:32:31.297-0700 INFO Listener address to use: 127.0.0.1

--new-log-timestamp=false restores the legacy seconds-since-start counter.

Security fixes

Three fixes in this release came through the private advisory process. Advisories are still in preparation; this section will be updated with their identifiers once they are published.

• Allocation quotas could be bypassed under --mobility. An authenticated client that repeatedly created a mobility allocation and disconnected had its quota released while the allocation, its relay socket and its ticket stayed alive, letting one user hold allocations well past --user-quota / --total-quota until the relay port range was exhausted. The charge is now held until final teardown. Regression coverage: examples/run_tests_mobility_quota.sh.
• DTLS allocated per-peer state before the cookie was verified. A ClientHello from an unverified (and possibly spoofed) source caused a full SSL, socket and session allocation before the source had proved return routability. The cookie exchange is now performed statelessly via DTLSv1_listen(), so an unanswered ClientHello leaves no state behind. This completes the hardening begun in 4.16.0.
• EVEN-PORT with the R bit clear leaked relay ports. The odd sibling port was reserved even when the client had not asked for it and was never released, so a server would eventually refuse new allocations that requested EVEN-PORT.

Upgrading is recommended for anyone running --mobility, DTLS, or accepting EVEN-PORT allocations.

What's Changed

• Free the secrets list on the get_user_key error paths
• Binding stateless fastpath
• Worktree stateless nonce mi fastpath
• Start the DTLS listeners only when --dtls is given
• Do not ask the kernel for an outgoing IP TTL of zero
• Drop --simple-log where it is a no-op alongside --log-file=stdout
• Fix localtime() data race in the logger
• Log format: ISO-8601 timestamp by default, no thread id, space delimiter
• Keep the legacy random nonce at 16 chars
• Emit exactly one log line per record
• Enable stateless nonce by default