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OpenSSL Insecure Protocol Negotiation Weakness

OpenSSL is prone to a remote protocol-negotiation weakness. This issue occurs because of the implementation of the 'SSL_OP_MSIE_SSLV2_RSA_PADDING' option to maintain compatibility with third-party software.

This issue presents itself when two peers try to negotiate the protocol they wish to communicate with. Attackers who can intercept and modify the SSL communications may exploit this weakness to force SSL version 2 to be chosen.

The attacker may then exploit various insecurities in SSL version 2 to gain access to or tamper with the cleartext communications between the targeted client and server.

Note that the 'SSL_OP_MSIE_SSLV2_RSA_PADDING' option is enabled with the frequently used 'SSL_OP_ALL' option.

SSL peers that are configured to disallow SSL version 2 are not affected by this issue.