+++ This bug was initially created as a clone of Bug #1154059 +++
We should disable the retry-with-SSL-3.0 behavior in curl because it can be trivially triggered by an on-path attacker to cause a protocol downgrade, and SSL 3.0 has several known weaknesses. This curl behavior is quite surprising because it is restricted to the NSS backend, and other systems which use the OpenSSL or GNUTLS backend do not share this behavior.
At this stage, it is best to leave SSL 3.0 enabled. (The in-protocol version negotiation has not been broken, sosome TLS version will be used automatically if supported by the server.)
This might reintroduce bug 525496 and bug 527771, so a system-wide knob to re-enable the SSL 3.0 fallback might be necessary. Perhaps the existence of a file like /etc/sysconfig/curl/enable-ssl-fallback could re-enable the old behavior.
The code in question has been removed from upstream libcurl:
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.