CVE-2020-26572

The TCOS smart card software driver in OpenSC before 0.21.0-rc1 has a stack-based buffer overflow in tcos_decipher.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

This flaw can be mitigated in cases where you can use opensc without the TCOS driver enabled. In such cases, the vulnerable driver can be disabled by specifying them in /etc/opensc.conf card_drivers field in allowlist fashion. One such example:

app default {
   card_drivers = cac, cac1, PIV-II;
}

This would only enable the cac, cac1, and PIV-II smart card drivers, and all others would be disabled, including the TCOS driver. With the TCOS driver disabled, this flaw is mitigated. It is important to list all drivers that you need in the card_drivers field so that they are not disabled too.