Such applications are affected if they use the option
SSL_OP_MSIE_SSLV2_RSA_PADDING. This option is implied by use of
SSL_OP_ALL, which is intended to work around various bugs in
third-party software that might prevent interoperability. The
SSL_OP_MSIE_SSLV2_RSA_PADDING option disables a verification step in
the SSL 2.0 server supposed to prevent active protocol-version
rollback attacks. With this verification step disabled, an attacker
acting as a "man in the middle" can force a client and a server to
negotiate the SSL 2.0 protocol even if these parties both support
SSL 3.0 or TLS 1.0. The SSL 2.0 protocol is known to have severe
cryptographic weaknesses and is supported as a fallback only.
Applications using neither SSL_OP_MSIE_SSLV2_RSA_PADDING nor
SSL_OP_ALL are not affected. Also, applications that disable
use of SSL 2.0 are not affected.