Severe memory constraint of wireless sensor networks (WSN) causes lots of problems such as irrecoverable stack overflow and out-of-memory failure. These problems motivated to develop efficient memory management schemes for WSNs. A shared-stack is the memory-efficient thread stack, designed for memory-constrained environments such as WSNs. However, stack switching of shared-stacks makes external memory fragmentation, which induces memory space overhead, or CPU overhead to eliminate it. In this paper, we propose a novel stack buffer management scheme for shared-stacks, called linked stack buffer management. It manages context of threads as multiple linked stack buffers. The simulation results demonstrate that the proposed scheme alleviates external fragmentation of shared-stacks efficiently.