Why do messages with long Base64 encoded lines pass GMS Anti-Virus?

Question

I have received a message where the Base64 encoded section consists of very long lines (993 bytes) with each line terminated by an illegal character.

Answer

The length of the lines are not in themselves a problem. Rather, it is the inclusion of the illegal character (in this case !) at the end of the line that is causing the attachment to be wrongly decoded.

As of build 3032 all illegal characters are correctly caught and ignored when decoding the Base64 mime section.

See Also:

• Why is it better to use GMS Anti-Virus rather than a third party anti-virus solution?

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