Out-of-bounds array write in Xpdf 4.05 and earlier, due to missing object type check in AcroForm field reference.
In Xpdf 4.05 (and earlier), a PDF object loop in the PDF resources leads to infinite recursion and a stack overflow.
Out-of-bounds array write in Xpdf 4.05 and earlier, triggered by an invalid character code in a Type 1 font. The root problem was a bounds check that was being optimized away by modern compilers.