- >= 2.5.5
Because Mail does not disallow CRLF in email addresses, an attacker can inject SMTP commands in specially crafted email addresses passed to RCPT TO and MAIL FROM.
Not affected by this vulnerability:
- Ruby 2.4.0+ with a fix for CVE-2015-9096.
- Applications that do not use SMTP delivery.
- Applications that validate email addresses to not include CRLF.
The injection attack is described in Terada, Takeshi. “SMTP Injection via Recipient Email Addresses.” 2015. The attacks described in the paper (Terada, p. 4) can be applied to the library without any modification.