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.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2026-55953)

Note that Nessus relies on the presence of the package as reported by the vendor.

The version of FreeBSD installed on the remote host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the 445c61c0-89e1-11f1-b35c-4c526214c986 advisory.

    https://github.com/erlang/otp/security/advisories/GHSA-c6cw-pr89-w882 reports:
    The OTP TLS/DTLS client (pre TLS-1.3) does not verify that               the cipher suite selected by the server in ServerHello is one               of those offered in ClientHello. A man-in-the-middle attacker               can select an anonymous cipher suite such as ECDH_anon that               was never offered by the client. Since anonymous suites do not               require a server certificate, this completely bypasses the               client's verify_peer setting, giving the attacker a fully               established connection without possessing any trusted               certificate, and thus complete read and modify access to the               transmitted data. TLS-1.3 is not affected.

Tenable has extracted the preceding description block directly from the FreeBSD security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
330402	Linux Distros Unpatched Vulnerability : CVE-2026-55953	Nessus	Misc.	critical
330268	FreeBSD : Erlang/OTP -- (D)TLS-1.2 server certificate verification bypass (445c61c0-89e1-11f1-b35c-4c526214c986)	Nessus	FreeBSD Local Security Checks	critical

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