From the Debian advisory:
Chaskiel M Grundman discovered that opensc, a library and utilities to
handle smart cards, would initialise smart cards with the Siemens CardOS M4
card operating system without proper access rights. This allowed everyone
to change the card's PIN.
With this bug anyone can change a user PIN without having the PIN or PUK
or the superusers PIN or PUK. However it can not be used to figure out the
PIN. If the PIN on your card is still the same you always had, there's a
resonable chance that this vulnerability has not been exploited.
This vulnerability affects only smart cards and USB crypto tokens based on
Siemens CardOS M4, and within that group only those that were initialised
with OpenSC. Users of other smart cards and USB crypto tokens, or cards
that have been initialised with some software other than OpenSC, are not