In Xpdf 4.05 (and earlier), a PDF object loop in a CMap, via the "UseCMap" entry, leads to infinite recursion and a stack overflow.
Exploitability
AV:LAC:HAT:NPR:NUI:NVulnerable System
VC:NVI:NVA:LSubsequent System
SC:NSI:NSA:N2.1/CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:NOther