CVE-2015-7511

Vulnerability

Libgcrypt versions before 1.6.5 improperly perform elliptic-point curve multiplication during ECDH decryption, leaking sensitive information through electromagnetic emanations [1]. This affects ECDH implementation used in GnuPG 2.1 and other applications [2]. The vulnerability is tracked as CVE-2015-7511.

Exploitation

An attacker with physical proximity to the target machine and ability to measure electromagnetic emanations can recover the ECDH private key. The attack requires the attacker to request decryption of a single carefully chosen ciphertext multiple times (a few dozen iterations), then apply time-frequency signal analysis on the captured EM leakage [1].

Impact

Successful exploitation allows the attacker to extract the full ECDH private decryption key, leading to compromise of encrypted communications and data confidentiality.

Mitigation

The vulnerability is fixed in Libgcrypt version 1.6.5, released on February 9, 2016 [2]. Users should upgrade to this version or later. Ubuntu and Fedora have also issued updated packages (USN-2896-1 [3] and Fedora updates respectively). No workaround exists without upgrading.