SMTP header injection
Summary: SMTP header injection occurs when user input is placed into email headers without adequate sanitization, letting an attacker inject additional headers with arbitrary values. PortSwigger notes the flaw can be exploited to send copies of emails to third parties, attach viruses, deliver phishing attacks, and alter email content, and is typically used by spammers borrowing the vulnerable company's reputation.
What's compelling: The issue is especially serious when the email carries sensitive information not meant for the attacker, such as a password reset token - a single unsanitized newline in a header field can hand over account recovery.
Read the original at PortSwigger Research ↗
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