Prerequisites:
The following blog posts/articles have explained e=3 Bleichenbacher's Signature Forgery attack clearly and can be useful:
- Filippo Valsorda's CVE --> This was a CVE by Filippo Valsorda on python-rsa module due to fault in implementation of signatures of PKCS#1 v1.5 padded messages
- Karabut's writeup for RSA CTF Challenge, Google CTF Quals 2017
- Hal Finney's write-up on Bleichenbacher's Signature Forgery
- Interesting explanation on Stack Exchange
Check out the original paper describing the attack by Daniel Bleichenbacher- http://archiv.infsec.ethz.ch/education/fs08/secsem/bleichenbacher98.pdf