CVE-2026-54887 — DTLS server cookie bypass during startup window due to empty initial cookie secret

Affected: Erlang OTP

Use of Default Cryptographic Key vulnerability in Erlang/OTP ssl (DTLS server) allows predictable DTLS cookie computation during the startup window, enabling source address verification bypass.

On DTLS server startup, dtls_server_connection:initial_hello/3 initializes previous_cookie_secret to the empty binary (<<>>) instead of a random value. Because HMAC with an empty key is deterministic, anyone who observes the plaintext ClientHello can compute dtls_handshake:cookie(<<>>, IP, Port, Hello) and forge a valid DTLS cookie before the first rotation of the cookie secret. The DTLS cookie (RFC 6347 §4.2.1) is a denial-of-service mitigation that prevents spoofed source IPs from forcing the server to allocate state and perform expensive cryptographic operations; it is not an authentication mechanism. During the window from server startup until the first secret rotation (0 to 15 seconds), an attacker who can observe the plaintext ClientHello can bypass the source address verification, enabling DTLS handshake amplification with spoofed source addresses.

This vulnerability is associated with program file lib/ssl/src/dtls_server_connection.erl and program routine dtls_server_connection:initial_hello/3.

This issue affects OTP from OTP 20.0 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssl from 8.2 before 11.7.3, 11.6.0.3 and 11.2.12.10.

USN-8901-1 — erlang vulnerabilities

Affected: Ubuntu:Pro:14.04:LTS: erlang, Ubuntu:Pro:16.04:LTS: erlang, Ubuntu:Pro:18.04:LTS: erlang, Ubuntu:Pro:20.04:LTS: erlang, Ubuntu:22.04:LTS: erlang, Ubuntu:24.04:LTS: erlang, Ubuntu:26.04:LTS: erlang

Wander Nauta discovered that Erlang incorrectly handled absolute paths when extracting zip archives. An attacker could possibly use this issue to write arbitrary files outside of the intended directory. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2025-4748)

It was discovered that the Erlang SFTP server did not properly limit the size of packets. A remote attacker could possibly use this issue to cause Erlang to use excessive resources, leading to a denial of service. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, and Ubuntu 18.04 LTS. (CVE-2025-26618)

It was discovered that the Erlang SSH server did not properly limit the length of algorithm names in key exchange messages. A remote attacker could possibly use this issue to cause Erlang to use excessive resources, leading to a denial of service. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, and Ubuntu 18.04 LTS. (CVE-2025-30211)

It was discovered that the Erlang TFTP server incorrectly handled certain file paths. A remote attacker could possibly use this issue to access files outside of the intended directory. (CVE-2026-21620)

It was discovered that the Erlang SFTP server incorrectly validated paths against the configured root directory. An authenticated user could possibly use this issue to access files outside of the root directory. (CVE-2026-23942)

It was discovered that the Erlang SSH server enabled zlib compression by default and did not limit…

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CVE-2026-54887 — DTLS server cookie bypass during startup window due to empty initial cookie secret

USN-8901-1 — erlang vulnerabilities