libcurl versions from 7.34.0 to before 7.64.0 are vulnerable to a heap out-of-bounds read in the code handling the end-of-response for SMTP.
If the buffer passed to `smtp_endofresp()` isn't NUL terminated and contains no character ending the parsed number, and `len` is set to 5, then the `strtol()` call reads beyond the allocated buffer. The read contents will not be returned to the caller.
Bug introduced by:
Name: Daniel Stenberg (the Curl project)
Upstream: Brian Carpenter (Geeknik Labs)
Created curl tracking bugs for this issue:
Affects: fedora-all [bug 1672906]
Do not use SMTP authentication with curl