CVE-2023-6135

The severity of the Network Security Services (NSS) package vulnerability is marked as moderate due to the inherent risk associated with a potential side-channel information leak. This flaw empowers a local attacker to capture a substantial volume of signature usages, providing a pathway for them to exploit this data to reconstruct portions of an ECDSA private key. The ECDSA private key is a fundamental component of cryptographic security, and a successful compromise could have severe implications for the confidentiality and integrity of sensitive information.

The side channel present in NSS is on the order of 20 to 50ns, measuring such small differences over the network, without ability to measure signature with the same nonce is not something anybody has shown as possible. The only reason we can measure such small differences in the Marvin attack (https://people.redhat.com/~hkario/marvin/) is because the attacker there has full control over the processed messages, as such can measure the same message over and over, with ECDSA NSS is generating the used nonce randomly, and internally, for each and every signature. So a possibility of a purely network attack is rather theoretical at this moment.