There is an invalid memory access vulnerability in the function TextPage::findGaps() located at TextOutputDev.c in Xpdf 4.01, which can (for example) be triggered by sending a crafted pdf file to the pdftops binary. It allows an attacker to cause Denial of Service (Segmentation fault) or possibly have unspecified other impact.
https://research.loginsoft.com/bugs/invalid-memory-access-in-textpagefindgaps-xpdf-4-01/