AccessControl/AuthEncoding.py in Zope before 2.13.19, as used in Plone before 4.2.3 and 4.3 before beta 1, allows remote attackers to obtain passwords via vectors involving timing discrepancies in password validation.
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.