Cross-border e-commerce (CBEC) involves online transactions between sellers and consumers across national borders. Despite increasing volatility in international trade, the CBEC market continues to grow, making it critical to understand how firms manage logistics uncertainty. This study investigates how internal and external uncertainties differently influence logistics service flexibility (LSF) and logistics information system (LIS) utilization. Using survey data from 214 CBEC professionals primarily located in Korea, structural equation modeling (SEM) reveals divergent patterns: (1) external uncertainties enhance logistics flexibility, whereas internal uncertainties show no significant direct effect; (2) internal uncertainties negatively affect LIS utilization, while external uncertainties show a marginally positive relationship; and (3) LIS utilization mediates the negative pathway from internal uncertainty to flexibility. These findings indicate that firms respond asymmetrically to uncertainty sources, challenging the view that uncertainty universally promotes digital adaptation. Framing LSF (reconfiguration) and LIS use (sensing/seizing) as distinct dynamic capabilities, our results show source-contingent activation: external turbulence catalyzes reconfiguration, whereas internal frictions dampen sensing/seizing, indirectly suppressing flexibility. By identifying an indirect-only (negative) pathway from internal uncertainty via LIS, we refine dynamic capability theory in CBEC logistics and delineate boundary conditions under which uncertainty does not automatically induce digital adaptation.