An Insufficient Entropy in PRNG vulnerability in Fortinet FortiOS 6.2.1 and below for device not enable hardware TRNG token and models not support builtin TRNG seed allows attacker to theoretically recover the long term ECDSA secret in a TLS client with a RSA handshake and mutual ECDSA authentication via the help of flush+reload side channel attacks in FortiGate VM models only.

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-15703
• https://fortiguard.com/psirt/FG-IR-19-186