An integer underflow was discovered in Fort 1.6.3 and 1.6.4 before 1.6.5. A malicious RPKI repository that descends from a (trusted) Trust Anchor can serve (via rsync or RRDP) a Manifest RPKI object containing an empty fileList. Fort dereferences (and, shortly afterwards, writes to) this array during a shuffle attempt, before the validation that would normally reject it when empty. This out-of-bounds access is caused by an integer underflow that causes the surrounding loop to iterate infinitely. Because the product is permanently stuck attempting to overshuffle an array that doesn't actually exist, a crash is nearly guaranteed.