X41 D-Sec GmbH Security Advisory: X41-2018-004
Confirmed Affected Versions: 0.1.9
Confirmed Patched Versions: -
Vendor: Yubico / Deprecated
Vendor URL: https://www.yubico.com/
Credit: X41 D-Sec GmbH, Eric Sesterhenn
An out of bounds write and read was discovered when malicious responses from a smartcard are received. These might lead to memory corruptions. We assume that these are not easily exploitable. X41 did not perform a full test or audit on the software. Please note that the library is deprecated for more than a year and no update will be published by the vendor.
This is a C library to interact with the CCID-part of the YubiKey NEO. There is a command line tool "ykneomgr" for interactive use. It supports querying the YubiKey NEO for firmware version, operation mode (OTP/CCID) and serial number. You may also mode switch the device and manage applets (list, delete and install).
Severity Rating: Medium
Vector: APDU Response
CVSS Score: 7.1 (High)
CVSS Vector: CVSS:3.0/AV:P/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
File lib/backend_pcsc.c contains the following code in function
There is an off-by-one write of a '\x00' when the sprintf() is called, since it terminates the string with a trailing null-byte. Additionally reads are performed based on this_len, which is retrieved from the data without further safety checks.
It is advised to migrate to YubiKey Manager since the vendor does not support the library anymore and will not issue a patch.
2018-02-03 Issues found
2018-05-22 Vendor contacted
2018-05-22 Vendor reply
2018-06-05 Requesting technical feedback from the vendor
2018-06-06 Vendor confirms bug, but states that library is depreciated, will not be fixed