In MatrixSSL 3.8.3 Open through 4.2.1 Open, the DTLS server mishandles incoming network messages leading to a heap-based buffer overflow of up to 256 bytes and possible Remote Code Execution in parseSSLHandshake in sslDecode.c. During processing of a crafted packet, the server mishandles the fragment length value provided in the DTLS message.

MatrixSSL 4.2.1 and earlier contains a timing side channel in ECDSA signature generation. This allows a local or a remote attacker, able to measure the duration of hundreds to thousands of signing operations, to compute the private key used. The issue occurs because crypto/pubkey/eccmath.c scalar multiplication leaks the bit length of the scalar.