EC private key file consumed via the d2i_ECPrivateKey function could cause a use after free condition. This, in turn, could cause a double free in several private key parsing functions (such as d2i_PrivateKey or EVP_PKCS82PKEY) and could lead to a DoS attack or memory corruption for applications that receive EC private keys from untrusted sources. This scenario is considered rare.
This issue affects all current OpenSSL versions: 1.0.2, 1.0.1, 1.0.0 and 0.9.8.
OpenSSL 1.0.2 users should upgrade to 1.0.2a OpenSSL 1.0.1 users should upgrade to 1.0.1m. OpenSSL 1.0.0 users should upgrade to 1.0.0r. OpenSSL 0.9.8 users should upgrade to 0.9.8zf.
This issue was discovered by the BoringSSL project and fixed in their commit 517073cd4b. The OpenSSL fix was developed by Matt Caswell of the OpenSSL