An issue was discovered in Mbed TLS 2.x before 2.28.7 and 3.x before 3.5.2. There was a timing side channel in RSA private operations. This side channel could be sufficient for a local attacker to recover the plaintext. It requires the attacker to send a large number of messages for decryption, as described in "Everlasting ROBOT: the Marvin Attack" by Hubert Kario.
Exploitability
AV:LAC:LPR:LUI:NScope
S:UImpact
C:HI:NA:N5.5/CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N