CVE-2026-55953— TLS 1.2 and DTLS client accepts unoffered anonymous cipher suite, bypassing server authentication

TLS 1.2 and DTLS client accepts unoffered anonymous cipher suite, bypassing server authentication

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 R13B03 before OTP 27.3.4.15, from OTP 28.0 before OTP 28.5.0.4, and from OTP 29.0 before OTP 29.0.4, corresponding to ssl from 3.10.7 before 11.2.12.11, from 11.3 before 11.6.0.4, and from 11.7 before 11.7.4. Whether OTP before OTP R13B03, corresponding to ssl before 3.10.7, is affected is unknown.

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

在会话协商时选择低安全性的算法(算法降级)

Erlang OTP 加密问题漏洞

Erlang OTP是瑞典Erlang社区的一套构建分布式系统的中间件平台。 Erlang OTP 17.0版本至29.0.4版本之前版本、28.5.0.4版本之前版本和27.3.4.15版本之前版本存在加密问题漏洞，该漏洞源于客户端在TLS握手过程中未验证服务器选择的密码套件是否属于客户端提供的套件，导致中间人攻击者可以利用匿名密钥交换套件，绕过证书验证和主机名检查，从而能够读取和修改应用流量。

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