The signature verification routines will crash with a NULL pointer dereference if presented with an ASN.1 signature using the RSA PSS algorithm and invalid parameters. Since these routines are used to verify certificate signature algorithms, this flaw can be used to crash any certificate verification operation and exploited in a DoS attack. Any application which performs certificate verification is vulnerable including OpenSSL clients and servers which enable client authentication.
This issue affects OpenSSL versions 1.0.2, and is fixed in version 1.0.2a.
Red Hat would like to thank the OpenSSL project for reporting this issue. Upstream acknowledges Stephen Henson of the OpenSSL development team as the original reporter.
This issue did not affect the versions of openssl as shipped with Red Hat Enterprise Linux 5, 6, and 7.