libxslt through 1.1.33 allows bypass of a protection mechanism because callers of xsltCheckRead and xsltCheckWrite permit access even upon receiving a -1 error code. xsltCheckRead can return -1 for a crafted URL that is not actually invalid and is subsequently loaded. In xsltCopyText in transform.c in libxslt 1.1.33, a pointer variable isn"t reset under certain circumstances. If the relevant memory area happened to be freed and reused in a certain way, a bounds check could fail and memory outside a buffer could be written to, or uninitialized data could be disclosed