Generating the ECDSA nonce k samples a random number r and then truncates this randomness with a modular reduction mod n where n is the order of the elliptic curve. Meaning k = r mod n. The division used during the reduction estimates a factor q_e by dividing the upper two digits (a digit having e.g. a size of 8 byte) of r by the upper digit of n and then decrements q_e in a loop until it has the correct size. Observing the number of times q_e is decremented through a control-flow revealing side-channel reveals a bias in the most significant bits of k. Depending on the curve this is either a negligible bias or a significant bias large enough to reconstruct k with lattice reduction methods. For SECP160R1, e.g., we find a bias of 15 bits.

An issue was discovered in wolfSSL before 5.7.0. A safe-error attack via Rowhammer, namely FAULT+PROBE, leads to ECDSA key disclosure. When WOLFSSL_CHECK_SIG_FAULTS is used in signing operations with private ECC keys, such as in server-side TLS connections, the connection is halted if any fault occurs. The success rate in a certain amount of connection requests can be processed via an advanced technique for ECDSA key recovery.

A malicious TLS1.2 server can force a TLS1.3 client with downgrade capability to use a ciphersuite that it did not agree to and achieve a successful connection. This is because, aside from the extensions, the client was skipping fully parsing the server hello. https://doi.org/10.46586/tches.v2024.i1.457-500

In function MatchDomainName(), input param str is treated as a NULL terminated string despite being user provided and unchecked. Specifically, the function X509_check_host() takes in a pointer and length to check against, with no requirements that it be NULL terminated. If a caller was attempting to do a name check on a non-NULL terminated buffer, the code would read beyond the bounds of the input array until it found a NULL terminator.This issue affects wolfSSL: through 5.7.0.