Erlang/OTP SSL DTLS Server Cookie Prediction Bypass Vulnerability (CVE-2026-54887)

EEF-CVE-2026-54887 Vulnerability Overview A DTLS server cookie bypass vulnerability occurs during the startup window due to the initial cookie key being empty. This vulnerability allows attackers to predict the DTLS cookie by observing the plaintext ClientHello, thereby bypassing source address verification and enabling DTLS handshake amplification attacks. Affected Versions Affected Versions: OTP from 20.0 to 29.0.3, 28.2.0.3, and 27.3.4.14; corresponding to ssl versions from 8.2 to 11.2.3, 11.6.0.3, and 11.2.12.10. Severity: CVSS v4 score of 6.3 (Medium). Remediation Fix Status: No specific fix is mentioned. Recommendations: Please report the issue at source. Detailed Information Vulnerability Description: - Using the default encryption key in Erlang/OTP ssl (DTLS server) allows the prediction of the DTLS cookie calculation during the startup window, thereby enabling source address verification bypass. - When the DTLS server starts, initializes to an empty binary ( ) instead of a random value. Since HMAC with an empty key is deterministic, anyone who observes the plaintext ClientHello can compute (IP, port, Hello) and forge a valid DTLS cookie before the cookie rotates for the first time. The DTLS cookie (RFC 6347 §4.2.1) is a denial-of-service mitigation measure designed to prevent spoofed source IPs from forcing the server to allocate stale resources and perform expensive cryptographic operations; it is not an authentication mechanism. Within the window from server startup to the first cookie rotation (0 to 15 seconds), an attacker can observe the plaintext ClientHello and bypass source address verification to execute a DTLS handshake amplification attack. Related Code: - This vulnerability is associated with the source file and the function . Database Specific Information

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Erlang/OTP SSL DTLS Server Cookie Prediction Bypass Vulnerability (CVE-2026-54887)