X509TrustManager in (1) Java Secure Socket Extension (JSSE) in SDK and JRE 1.4.0 through 1.4.0_01, (2) JSSE before 1.0.3, (3) Java Plug-in SDK and JRE 1.3.0 through 1.4.1, and (4) Java Web Start 1.0 through 1.2 incorrectly calls the isClientTrusted method when determining server trust, which results in improper validation of digital certificate and allows remote attackers to (1) falsely authenticate peers for SSL or (2) incorrectly validate signed JAR files.