New SSL Security Issues: A vulnerability allowing hijacking of an already connected SSL 3.0 (TLS 1.0) sessions has been disclosed.
SSL technology provides an end-to-end secure communications tunnel used most commonly by the HTTPS protocol. This, most recent, vulnerability allows an attacker to insert text of their choice into the data-stream, even after the secure handshake has occurred. This is another security gap created by the standard’s renegotiation process that is intended to allow a new SSL connection to be established over an already connected SSL session.
SSL renegotiation is most useful in the following situations: when client authentication is required, to use a different set of encryption and decryption keys, or when the server wants to switch encryption or hashing algorithms. For now, some patches have been made available that disable this functionality completely in order to avoid the vulnerability.
It will probably be a few weeks until patches including a reworked renegotiation mechanism appear. Most importantly, a fix has been in the works (by most browser vendors) but it won’t be out until the respective vendors finish their work. So, don’t depend on SSL until your browser is patched.