A flaw was found in Mozilla nss. Raccoon attack exploits a flaw in the TLS specification which can lead to an attacker being able to compute the pre-master secret in connections which have used a Diffie-Hellman (DH) based ciphersuite. In such a case this would result in the attacker being able to eavesdrop on all encrypted communications sent over that TLS connection. The highest threat from this vulnerability is to data confidentiality.
Created nss tracking bugs for this issue:
Affects: fedora-all [bug 1877558]
NSS as shipped with Red Hat Enterprise Linux 6, 7, and 8 does not re-use Diffie-Hellman Ephemeral (DHE) keys. It reuses Elliptic Curve Diffie-Hellman Ephemeral (ECDHE) keys by default, but Attacking ECDH and ECDHE cipher suites are not in the scope of the Raccoon Attack and generally considered to be unaffected . Further, reuse of ECDHE keys can be disabled starting in nss 3.17 .
For these reasons, Red Hat Product Security has marked the Severity of this flaw as Low. Please see  for more information about Low Severity ratings.
1. https://raccoon-attack.com/RacoonAttack.pdf pg. 13
Thorough Explanation can be found: https://raccoon-attack.com/RacoonAttack.pdf
Raccoon Attack: Finding and Exploiting Most-Significant-Bit-Oracles in TLS-DH(E) by Robert Merget, Marcus Brinkmann, et al.
Any risk involving ECDHE key reuse on the nss server can be mitigated by setting the SSL_REUSE_SERVER_ECDHE_KEY socket option to PR_FALSE.