Race condition in Download Manager in Android 4.x before 4.4.4, 5.0.x before 5.0.2, 5.1.x before 5.1.1, and 6.x before 2016-04-01 allows attackers to bypass private-storage file-access restrictions via a crafted application that changes a symlink target, as demonstrated by obtaining Signature or SignatureOrSystem access, aka internal bug 26211054.
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.