Service termination via pre-cookie DTLS state retention
Published Aug 11, 2026 · Updated Aug 11, 2026
Memory exhaustion in coturn before 4.16.0 allows remote attackers to terminate the TURN service via fragmented DTLS ClientHellos. The DTLS listener retains per-peer OpenSSL session state while OpenSSL zeroes a reassembly bitmask sized from an attacker-declared 650,000-byte handshake before cookie validation. Exploitation requires certificate-backed DTLS, but no TURN credentials, valid cookie, completed handshake, source spoofing, or response processing; sustained fresh UDP tuples exhaust memory and stop active relays.
Summary
What happened
Memory exhaustion in coturn before 4.16.0 allows remote attackers to terminate the TURN service via fragmented DTLS ClientHellos. The DTLS listener retains per-peer OpenSSL session state while OpenSSL zeroes a reassembly bitmask sized from an attacker-declared 650,000-byte handshake before cookie validation. Exploitation requires certificate-backed DTLS, but no TURN credentials, valid cookie, completed handshake, source spoofing, or response processing; sustained fresh UDP tuples exhaust memory and stop active relays.
The record
- CVE
- CVE-2026-73214
- Published
- Aug 11, 2026
- Updated
- Aug 11, 2026
- Vendor
- coturn
- Product
- coturn
- Classifications
- CWE-770, CWE-400, T1499.003
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 11, 2026CVE publishedPublication date reported by the CVE source.
- Aug 11, 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.
- Affected versionversion=< 4.16.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- Fragmented DTLS ClientHello reproductionfunctional · demonstrated
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Technologies
Your stack
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Your stack
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