Описание
The Erlang/OTP ssl TLS 1.2 (and earlier) and DTLS client does not verify that the cipher suite selected by the server in ServerHello was among the suites offered by the client in ClientHello. The client-side tls_handshake:hello/5 handler validates the negotiated protocol version and the downgrade sentinel but hands the server-chosen suite directly to ssl_handshake:handle_server_hello_extensions/9, which installs it without a membership check. The TLS 1.3 client path performs this check (per RFC 8446), so it is not affected. An on-path attacker between the client and the intended server can respond with a ServerHello selecting an anonymous key exchange suite such as TLS_DH_anon_* or TLS_ECDH_anon_* that the client never offered. Anonymous suites do not require the server to present a certificate, so the entire verify_peer and cacerts configuration is bypassed: the attacker completes the handshake with its own ephemeral parameters, no certificate is validated, no hostname is checked, and ssl:connect returns {ok, Socket}. All subsequent application traffic is readable and modifiable by the attacker. This issue affects OTP from OTP 17.0 before OTP 29.0.4, OTP 28.5.0.4 and OTP 27.3.4.15, corresponding to ssl from 5.3.4 before 11.7.4, 11.6.0.4 and 11.2.12.11.
Пакеты
| Пакет | Статус | Версия исправления | Релиз | Тип |
|---|---|---|---|---|
| erlang | fixed | 1:29.0.4+dfsg-1 | package |
Примечания
https://github.com/erlang/otp/security/advisories/GHSA-c6cw-pr89-w882
https://cna.erlef.org/cves/CVE-2026-55953.html
https://osv.dev/vulnerability/EEF-CVE-2026-55953
Introduced with: https://github.com/erlang/otp/commit/84adefa331c4159d432d22840663c38f155cd4c1 (OTP_R13B03)
Fixed by: https://github.com/erlang/otp/commit/e6ff938116b2872bccc478af7fefb56627285b77 (OTP-27.3.4.15)
Fixed by: https://github.com/erlang/otp/commit/0a82596d425abe43dc2e0b3d74aa1557ef74051c (OTP-28.5.0.4)
Fixed by: https://github.com/erlang/otp/commit/064e236414614f9085cbbbd6eacf0e43c02d1b4b (OTP-29.0.4)
EPSS
Связанные уязвимости
The Erlang/OTP ssl TLS 1.2 (and earlier) and DTLS client does not verify that the cipher suite selected by the server in ServerHello was among the suites offered by the client in ClientHello. The client-side tls_handshake:hello/5 handler validates the negotiated protocol version and the downgrade sentinel but hands the server-chosen suite directly to ssl_handshake:handle_server_hello_extensions/9, which installs it without a membership check. The TLS 1.3 client path performs this check (per RFC 8446), so it is not affected. An on-path attacker between the client and the intended server can respond with a ServerHello selecting an anonymous key exchange suite such as TLS_DH_anon_* or TLS_ECDH_anon_* that the client never offered. Anonymous suites do not require the server to present a certificate, so the entire verify_peer and cacerts configuration is bypassed: the attacker completes the handshake with its own ephemeral parameters, no certificate is validated, no hostname is checked, ...
A flaw was found in the Erlang/OTP ssl client. This vulnerability allows an on-path attacker to bypass server authentication in TLS 1.2 (and earlier) and DTLS connections. By tricking the client into accepting an unoffered anonymous cipher suite, the attacker can complete the handshake without a valid server certificate. This enables the attacker to read and modify all subsequent application traffic, leading to significant information disclosure and integrity compromise.
The Erlang/OTP ssl TLS 1.2 (and earlier) and DTLS client does not verify that the cipher suite selected by the server in ServerHello was among the suites offered by the client in ClientHello. The client-side tls_handshake:hello/5 handler validates the negotiated protocol version and the downgrade sentinel but hands the server-chosen suite directly to ssl_handshake:handle_server_hello_extensions/9, which installs it without a membership check. The TLS 1.3 client path performs this check (per RFC 8446), so it is not affected. An on-path attacker between the client and the intended server can respond with a ServerHello selecting an anonymous key exchange suite such as TLS_DH_anon_* or TLS_ECDH_anon_* that the client never offered. Anonymous suites do not require the server to present a certificate, so the entire verify_peer and cacerts configuration is bypassed: the attacker completes the handshake with its own ephemeral parameters, no certificate is validated, no hostname is checked, an
EPSS