This vulnerability arises because the function tls_gen_connection:handle_protocol_record/3 in Erlang/OTP's ssl module rejects APPLICATION_DATA records during pre-handshake states only when acting as a server, but not when acting as a client. Consequently, a network-positioned attacker can send unauthenticated plaintext APPLICATION_DATA records to the client during the handshake. These records are buffered and delivered post-handshake as if authenticated, enabling blind injection of data. The injection window is larger for TLS versions prior to 1.3 than for TLS 1.3. Affected versions include OTP from 17.0 before 29.0.3, 28.5.0.3, and 27.3.4.14, corresponding to ssl versions 5.3.4 before 11.7.3, 11.6.0.3, and 11.2.12.10. TLS 1.3 support introduced in OTP 22.0 is also affected.

An attacker positioned on the network can inject unauthenticated plaintext data into the TLS client during the handshake. The client buffers this data and delivers it after handshake completion as if it were authenticated server data. The attacker cannot observe the client's response or influence the connection further, so the impact is limited to blind injection of unauthenticated bytes. This could potentially lead to application-level confusion or protocol desynchronization but does not allow data disclosure or connection takeover.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary workaround is indicated in the provided data. Users should monitor Erlang/OTP vendor advisories for updates and apply patches once available. Until then, be aware of the risk of unauthenticated data injection during TLS handshakes in affected versions.