Key Exchange Impersonation in Erlang/OTP ssl (CVE-2026-89422)
CVSS 4.0
9.3critical
EPSS
—
Published
()
Modified
AI analysis
CVE-2026-89422 exposes Erlang/OTP ssl with a Key Exchange without Entity Authentication flaw. A TLS 1.3 client connection can be impersonated by answering a pre_shared_key extension the server never offered, causing the handshake to complete without validating the server certificate. This bypasses certificate validation, hostname verification, partial chain checking, CRL checking, and OCSP stapling, allowing an attacker to establish a valid-looking connection against a certificate-less, key-less peer. The vulnerability affects all default client configurations and is not restricted to TLS 1.2 clients. No public exploit is known, and the issue is reported as critical with no confirmed exploitation.
What to do: Upgrade all affected Erlang/OTP ssl versions to the latest fixed release; disable TLS 1.3 with PSK extensions or restrict clients to TLS 1.2; verify certificate and hostname validation; monitor for resumption-based impersonation and certificate validation bypass.
Affected
Erlang/OTP ssl
OTP 22.2 before OTP 27.3.4.18, OTP 28.5.0.7, and OTP 29.1.1; ssl 9.5 before 11.2.12.13, 11.6.0.6, and 11.7.7
Estimated exposure
largelarge (100k-1M users or 10k-100k systems) — No concrete installation counts are available; based on the default client configuration being affected and OTP ssl being widely deployed, the exposure is estimated as large, plausibly spanning many devices/systems.
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
Key Exchange without Entity Authentication vulnerability in Erlang/OTP ssl allows a peer that answers a TLS 1.3 client connection to impersonate the intended server. A pre_shared_key extension in the ServerHello that the client never offered causes the client to complete the handshake without validating the server's certificate, so ssl:connect returns {ok, Socket} against a peer holding no certificate, no private key and no prior session. tls_client_connection_1_3:handle_server_hello/2 passes the received extension to tls_gen_connection_1_3:handle_resumption/2, which sets resumption = true on its mere presence without checking that the client offered a PSK. tls_handshake_1_3:get_pre_shared_key/4 meanwhile falls back to the all-zero "no PSK" value and keys the handshake with the ordinary non-PSK schedule, so the attacker's own ephemeral key suffices. The resumption flag then routes maybe_resumption/1 straight to wait_finished, skipping the certificate-handling states, so certificate path validation, verify_fun, hostname verification, partial_chain, CRL checking and OCSP stapling are all bypassed. The default client configuration is affected; clients restricted to TLS 1.2 are not. This issue affects OTP from OTP 22.2 before OTP 27.3.4.18, OTP 28.5.0.7, and OTP 29.1.1, corresponding to ssl from 9.5 before 11.2.12.13, 11.6.0.6, and 11.7.7.
Canadian Cyber Centre warns Erlang/OTP is affected by CVE-2026-65634 and CVE-2026-89422 and urges updates.
The Canadian Centre for Cyber Security published advisory AV26-948 stating that Erlang/OTP is affected by vulnerabilities tracked as CVE-2026-65634 and CVE-2026-89422. The notice lists multiple OTP release lines and commits that are fixed only in later builds, including 27.3.4.18, 28.5.0.7, and 29.1.1. Administrators are urged to review the linked erlang/otp GitHub security advisories and apply updates. No exploitation is described.