CVE-2020-26572

2020-10-0711:07:52

redhat.com

access.redhat.com

opensc

smart card driver

buffer overflow

mitigation

opensc.conf

CVSS2

2.1

Attack Vector

LOCAL

Attack Complexity

LOW

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

PARTIAL

AV:L/AC:L/Au:N/C:N/I:N/A:P

CVSS3

5.5

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS

0.001

Percentile

19.0%

JSON

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

Mitigation

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.