ECDSA P-256 private key recovery in OpenSSL

1) Information disclosure

EUVDB-ID: #VU4133

Risk: Low

CVSSv3.1: 4.8 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2016-7056

CWE-ID: CWE-310 - Cryptographic Issues

Exploit availability: No

Description

The vulnerability allows a local user obtain potentially sensitive information.

The vulnerability exists due the OpenSSL does not properly set the BN_FLG_CONSTTIME for nonces when signing with the P-256 elliptic curve in ecdsa_sign_setup() function in crypto/ec/ecdsa_ossl.c. A local attacker can conduct a cache-timing attack and recover ECDSA P-256 private keys

Successful exploitation of this vulnerability may allow an attacker to obtain potentially sensitive information.

The vulnerability is discovered in OpenSSL 1.0.1u. Other versions may also be affected.

Mitigation

Install update from vendor's website.

Vulnerable software versions

OpenSSL: 1.0.1u

External links

http://eprint.iacr.org/2016/1195

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.