CVE-2026-54887 DTLS server cookie bypass during startup window due to empty initial cookie secret
Attackers can bypass DTLS source address verification during server startup, enabling amplification attacks and denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-54887?
CVE-2026-54887 is a medium-severity vulnerability in Erlang OTP, published on 2 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-1394
Which versions are affected by CVE-2026-54887?
It affects 2 products.
Products include Erlang Erlang\/Otp, Erlang Erlang\/Ssl.
How do I fix CVE-2026-54887?
Upgrade to a fixed version.
Is CVE-2026-54887 being exploited?
There is no known exploitation of CVE-2026-54887 in the wild and no public exploit code.
Other vulnerabilities in Erlang OTP
- CVE-2022-37026 Auth bypass in n/a
- CVE-2016-10253 Memory corruption in n/a
- CVE-2026-55953 TLS 1.2 and DTLS client accepts unoffered anonymous cipher suite, bypassing server authentication
- CVE-2026-49759 Stack buffer overflow in SCTP error cause parsing in inet_drv allows remote VM crash
- CVE-2026-58227 TLS/DTLS denial of service via unbounded recursion on cross-signed peer certificate chain
Sources
Also known as AZL-95660, DEBIAN-CVE-2026-54887, EEF-CVE-2026-54887, GHSA-p2m2-3c2w-8jp8, UBUNTU-CVE-2026-54887.