Vulnerability · Published Jul 2, 2026 · Assigned by EEF
CVE-2026-54887DTLS server cookie bypass during startup window due to empty initial cookie secret
Medium 6.3
In plain English
A medium-severity security flaw in OTP from Erlang. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 16% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | erlang | no fix listed | DEBIAN-CVE-2026-54887 |
| Debian:13 | erlang | 1:27.3.4.1+dfsg-1+deb13u3 | DEBIAN-CVE-2026-54887 |
| Debian:14 | erlang | 1:29.0.3+dfsg-1 | DEBIAN-CVE-2026-54887 |
| Ubuntu:22.04:LTS | erlang | 1:24.2.1+dfsg-1ubuntu0.8 | UBUNTU-CVE-2026-54887 |
| Ubuntu:22.04:LTS | erlang | 1:24.2.1+dfsg-1ubuntu0.8 | USN-8901-1 |
| Ubuntu:24.04:LTS | erlang | 1:25.3.2.8+dfsg-1ubuntu4.8 | USN-8901-1 |
| Ubuntu:24.04:LTS | erlang | 1:25.3.2.8+dfsg-1ubuntu4.8 | UBUNTU-CVE-2026-54887 |
| Ubuntu:25.10 | erlang | no fix listed | UBUNTU-CVE-2026-54887 |
| Ubuntu:26.04:LTS | erlang | 1:27.3.4.6+dfsg-1ubuntu0.2 | USN-8901-1 |
| Ubuntu:26.04:LTS | erlang | 1:27.3.4.6+dfsg-1ubuntu0.2 | UBUNTU-CVE-2026-54887 |
Affected products (as reported)
Weakness: CWE-1394 · 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
References
- https://github.com/erlang/otp/security/advisories/GHSA-p2m2-3c2w-8jp8 vendor-advisory, related
- https://cna.erlef.org/cves/CVE-2026-54887.html related
- https://osv.dev/vulnerability/EEF-CVE-2026-54887 related
- https://www.erlang.org/doc/system/versions.html#order-of-versions x_version-scheme
- https://github.com/erlang/otp/commit/888e3bcd72d5406016b9e0de741026bc2a6f114d patch