CVE-2016-0702

La función MOD_EXP_CTIME_COPY_FROM_PREBUF en crypto/bn/bn_exp.c en OpenSSL 1.0.1 en versiones anteriores a 1.0.1s y 1.0.2 en versiones anteriores a 1.0.2g no considera correctamente las veces que se accede al cache-bank durante la exponenciación modular, lo que facilita a usuarios locales descubrir las claves RSA ejecutando una aplicación manipulada en el mismo núcleo de la CPU Intel Sandy Bridge como víctima y aprovechándose de los conflictos del cache-bank, también conocida como un ataque "CacheBleed".

A side-channel attack was found that makes use of cache-bank conflicts on the Intel Sandy-Bridge microarchitecture. An attacker who has the ability to control code in a thread running on the same hyper-threaded core as the victim's thread that is performing decryption, could use this flaw to recover RSA private keys.

Yuval Yarom, Daniel Genkin, and Nadia Heninger discovered that OpenSSL was vulnerable to a side-channel attack on modular exponentiation. On certain CPUs, a local attacker could possibly use this issue to recover RSA keys. This flaw is known as CacheBleed. Adam Langley discovered that OpenSSL incorrectly handled memory when parsing DSA private keys. A remote attacker could use this issue to cause OpenSSL to crash, resulting in a denial of service, or possibly execute arbitrary code. Various other issues were also addressed.