CVE-2021-4160

There is a carry propagation bug in the MIPS32 and MIPS64 squaring
procedure. Many EC algorithms are affected, including some of the TLS 1.3
default curves. Impact was not analyzed in detail, because the
pre-requisites for attack are considered unlikely and include reusing
private keys. Analysis suggests that attacks against RSA and DSA as a
result of this defect would be very difficult to perform and are not
believed likely. Attacks against DH are considered just feasible (although
very difficult) because most of the work necessary to deduce information
about a private key may be performed offline. The amount of resources
required for such an attack would be significant. However, for an attack on
TLS to be meaningful, the server would have to share the DH private key
among multiple clients, which is no longer an option since CVE-2016-0701.
This issue affects OpenSSL versions 1.0.2, 1.1.1 and 3.0.0. It was
addressed in the releases of 1.1.1m and 3.0.1 on the 15th of December 2021.
For the 1.0.2 release it is addressed in git commit 6fc1aaaf3 that is
available to premium support customers only. It will be made available in
1.0.2zc when it is released. The issue only affects OpenSSL on MIPS
platforms. Fixed in OpenSSL 3.0.1 (Affected 3.0.0). Fixed in OpenSSL 1.1.1m
(Affected 1.1.1-1.1.1l). Fixed in OpenSSL 1.0.2zc-dev (Affected
1.0.2-1.0.2zb).

Notes