The Render extension in XFree86 4.0.1, X.Org X Window System (aka X11 or X) X11R6.7, and X.Org Server (aka xserver and xorg-server) before 1.16.3 allows remote authenticated users to cause a denial of service (out-of-bounds read or write) or possibly execute arbitrary code via a crafted length or index value to the (1) ProcRenderQueryVersion, (2) SProcRenderQueryVersion, (3) SProcRenderQueryPictFormats, (4) SProcRenderQueryPictIndexValues, (5) SProcRenderCreatePicture, (6) SProcRenderChangePicture, (7) SProcRenderSetPictureClipRectangles, (8) SProcRenderFreePicture, (9) SProcRenderComposite, (10) SProcRenderScale, (11) SProcRenderCreateGlyphSet, (12) SProcRenderReferenceGlyphSet, (13) SProcRenderFreeGlyphSet, (14) SProcRenderFreeGlyphs, or (15) SProcRenderCompositeGlyphs function.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.