CVE-2015-2741

Mozilla Firefox anterior a 39.0, Firefox ESR 38.x anterior a 38.1, y Thunderbird anterior a 38.1 no refuerzan la fijación (pinning) de las claves cuando encuentre un problema con los certificados X.509 que genere un dialogo de usuario, lo que permite a atacantes man-in-the-middle asistidos por usuario evadir las restricciones de acceso mediante la provocación de (1) un certificado caducado o (2) un nombre de anfitrión malasociado para un dominio con la fijación (pinning) habilitado.

It was found that Firefox skipped key-pinning checks when handling an error that could be overridden by the user (for example an expired certificate error). This flaw allowed a user to override a pinned certificate, which is an action the user should not be able to perform.

USN-2656-1 fixed vulnerabilities in Firefox for Ubuntu 14.04 LTS and later releases. This update provides the corresponding update for Ubuntu 12.04 LTS. Karthikeyan Bhargavan discovered that NSS incorrectly handled state transitions for the TLS state machine. If a remote attacker were able to perform a man-in-the-middle attack, this flaw could be exploited to skip the ServerKeyExchange message and remove the forward-secrecy property. Looben Yan discovered 2 use-after-free issues when using XMLHttpRequest in some circumstances. If a user were tricked in to opening a specially crafted website, an attacker could potentially exploit these to cause a denial of service via application crash, or execute arbitrary code with the privileges of the user invoking Firefox. Various other issues were also addressed.