Python mail SMTP Parser DoS via Negative Literal Count and Fix

Vulnerability Overview Vulnerability Type: Denial of Service (DoS) Vulnerability Vulnerability Description: When the parser encounters an SMTP command containing a negative literal count, it rejects the command and raises a exception. This may allow a malicious client to cause a denial of service to the server by sending commands with negative literal counts. Impact Scope Affected Component: SMTP parser in the module Affected Versions: Not explicitly specified, but inferred from commit history to be specific versions containing this vulnerability Remediation Fix Method: Add validation in the parser to check for negative literal counts. Upon encountering such cases, the parser raises a exception to reject the command. Fix Code: ```python def test_literalNegativeCount(self): """A literal with a negative count is rejected with a ValueError instead of causing the parser into a non-terminating loop.""" self.server.handleData(b"MAIL FROM:\r\n") self.server.handleData(b"RCPT TO:\r\n") self.server.handleData(b"DATA\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server.handleData(b"1\r\n") self.server

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Python mail SMTP Parser DoS via Negative Literal Count and Fix

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