Contributes to hydrolyze hemicellulose, the major component of plant cell-walls. XLNA and XLNB seem to act sequentially on the substrate to yield xylobiose and xylose as carbon sources. Endohydrolysis of (1->4)-beta-D-xylosidic linkages in xylans. Glycan degradation; xylan degradation. Belongs to the glycosyl hydrolase 10 (cellulase F) family.