CVE-2026-54887
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 29.0.3, 28.5.0.3 and 27.3.4.14 corresponding to ssl from 8.2 before 11.7.3, 11.6.0.3 and 11.2.12.10.
Scoring
- Severity
- MEDIUM
- CVSS base score
- 6.3
- CVSS vector
- CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- EPSS probability
- 0.24%
- CWE
- CWE-1394
- Published
- 2026-07-02
- Last modified
- 2026-07-24
Affected products
- Erlang OTP
- Erlang OTP
- Erlang OTP
Weakness type
Related vulnerabilities
- CVE-2026-75870 — Punk versions before 0.18 for Perl allow session cookie forgery via an empty default HMAC key when a session is declared without a secret
- CVE-2026-5039 — Predictable Default Cryptographic Key Used for DES Encryption in TP-Link TL-WL841N
- CVE-2026-20709 — Use of Default Cryptographic Key in the hardware for some Intel(R) Pentium(R) Processor Silver...
- CVE-2026-2215 — rachelos WeRSS we-mp-rss JWT auth.py default key
- CVE-2026-25815 — Fortinet FortiOS through 7.6.6 allows attackers to decrypt LDAP credentials stored in device...
- CVE-2025-41742 — Sprecher Automation: SPRECON-E series has a critical vulnerability due to the use of static cryptographic keys in system components
- CVE-2025-41744 — Sprecher Automation: SPRECON-E series has static default key material for TLS connections
- CVE-2025-55049 — Use of Default Cryptographic Key (CWE-1394)