Executive brief
Email::Sender::Transport::Sendmail is a Perl library used to send emails via the sendmail program. On Windows systems, it constructs a shell command line to invoke sendmail with envelope addresses (sender, recipients) taken from email headers. An attacker who controls the From, To, or Cc header of an email can inject shell metacharacters to execute arbitrary commands on the sending system.
Technical details
The vulnerability is a command injection affecting Windows (MSWin32) only. On Windows, the transport builds a shell command string containing the envelope sender and recipients, which are passed to open() where they reach cmd.exe; other platforms pass arguments as a list and are not affected. An attacker controlling email headers can inject shell metacharacters like & and | into addresses, leading to arbitrary command execution with the privileges of the sending process. The fix (version 2.602+) validates envelope addresses against a strict pattern and rejects non-compliant addresses before constructing the command.
Affected products
- Perl Email::Sender::Transport::Sendmail before 2.602
Timeline
- 2026-09-21: disclosed