OpenSSL patched three vulnerabilities in its latest release , Out Of the three bugs, only one was rated high severity and could lead to OpenSSL crashes. This high vulnerability is a heap-based buffer overflow bug (CVE-2016-7054) related to Transport Layer Security (TLS) connections using *-CHACHA20-POLY1305 cipher suites.Only OpenSSL 1.1.0 is affected, earlier versions are not. Users should upgrade to OpenSSL 1.1.0c.
This vulnerability, reported by Robert Święcki of the Google Security Team on September 25, can lead to DoS attack by corrupting larger payloads, resulting in a crash of OpenSSL.
The OpenSSL project also patches a moderate severity vulnerability (CVE-2016-7053) that can cause applications to crash.
“Applications parsing invalid CMS structures can crash with a NULL pointer dereference. This is caused by a bug in the handling of the ASN.1 CHOICE type in OpenSSL 1.1.0 which can result in a NULL value being passed to the structure callback if an attempt is made to free certain invalid encodings. Only CHOICE structures using a callback which do not handle NULL value are affected.” OpenSSL Project team described.
This bug too affects only OpenSSL 1.1.0, and users should upgrade to 1.1.0c.
The third vulnerability was rated low severity, which is related to the Broadwell-specific Montgomery multiplication procedure that handles input lengths divisible by, but longer than, 256 bits , OpenSSL, said.
Analysis suggests that attacks against RSA, DSA and DH private keys are impossible. This is because the subroutine in question is not used in operations with the private key itself and an input of the attacker’s direct choice. Otherwise the bug can manifest itself as transient authentication and key negotiation failures or reproducible erroneous outcome of public-key operations with specially crafted input.
This issue was publicly reported as transient failures and was not initially recognized as a security issue. This issue does not affect OpenSSL versions prior to 1.0.2. Due to the low severity of this defect we are not issuing a new 1.0.2 release at this time.
The team did not issue an update at this time. The fix will be included in the next 1.0.2 release. So, users are recommended to wait for it.
Impact was not analyzed in detail, because pre-requisites for attack are considered unlikely. Namely multiple clients have to choose the curve in question and the server has to share the private key among them, neither of which is default behaviour. Even then only clients that chose the curve will be affected.