Mbed TLS before 3.6.4 has a PEM parsing one-byte heap-based buffer underflow, in mbedtls_pem_read_buffer and two mbedtls_pk_parse functions, via untrusted PEM input.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:LI:NA:L4.8/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:LOther