CVE-2009-4123

Vulnerability

The jruby-openssl gem, prior to version 0.6, contains a critical flaw in its SSL certificate validation logic. When an application uses OpenSSL::SSL::VERIFY_PEER mode, the library incorrectly handles failed certificate verification, effectively ignoring the failure and silently accepting invalid certificates. This vulnerability stems from improper implementation of the peer verification callback, which fails to enforce the security policy intended by the developer [4].

Exploitation

An attacker can exploit this vulnerability by presenting a rogue SSL certificate to a vulnerable client or server. For client applications using net/https with peer verification enabled, an attacker positioned on the network can intercept the connection and present a self-signed or fraudulent certificate. Since the verification failure is silently ignored, the client application accepts the connection as legitimate. Similarly, server applications that validate client certificates are also affected, allowing an attacker to present a dummy certificate and gain unauthorized access [4]. No special privileges are required; the attacker only needs network access to intercept traffic.

Impact

Successful exploitation undermines the security of any SSL/TLS connection relying on certificate validation. For client-side scenarios, an attacker can perform man-in-the-middle attacks to eavesdrop on, modify, or inject data into the supposedly secure channel. For server-side scenarios, an attacker can impersonate a legitimate client or bypass client authentication. This compromises the confidentiality, integrity, and authenticity of communications, potentially affecting any application that depends on jruby-openssl for secure connections [1][4].

Mitigation

The vulnerability is fixed in jruby-openssl version 0.6. Users should upgrade by running jruby -S gem install jruby-openssl to obtain the patched version. A patch is also available for version 0.5.2. No workarounds are known other than switching to a different SSL library [4].