It's not a great bug, but I think it would require a very particular set of circumstances to arise: > ... only certificates with valid signatures trigger ASN.1

It's not a great bug, but I think it would require a very particular set of circumstances to arise: > ... only certificates with valid signatures trigger ASN.1 re-encoding and hence the bug. Specifically, since OpenSSL's default TLS X509 chain verification code verifies the certificate chain from root to leaf, TLS handshakes could only be targeted with valid certificates issued by trusted Certification Authorities. However it does seem like a great exploit method for malware, using legit signed certificates that allow overwriting memory just by parsing the cert.