SQL injection via the :comment option in Postgrex.stream/4

Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection') vulnerability in elixir-ecto postgrex allows SQL Injection via the :comment option of Postgrex.stream/4. An attacker who can influence that value can close the comment delimiter with */ and extend the streamed statement with their own clauses, which execute under the connection's role. Ecto exposes the same option through Ecto.Repo.stream/2.

Postgrex appends the comment by concatenating it into the statement text sent in the Parse message, without escaping or rejecting */. The option is validated by comment_not_present!/1 at every other execution point; stream/4 never calls it. Because Parse accepts a single command, the injection is confined to the streamed statement and further statements cannot be chained.

This issue affects postgrex: from 0.19.3 before 0.22.4.

Reject any :comment value containing */ or a null byte before passing it to Postgrex.stream/4 or Ecto.Repo.stream/2. Alternatively, build comments only from trusted values.

The application must pass a :comment derived from untrusted input to Postgrex.stream/4 or Ecto.Repo.stream/2. Applications that omit the option or pass only static values are unaffected.