Contiki-NG is an operating system for Internet of Things devices. An off-by-one error can be triggered in the Antelope database management system in the Contiki-NG operating system in versions 4.8 and prior. The problem exists in the Contiki File System (CFS) backend for the storage of data (file os/storage/antelope/storage-cfs.c). In the functions "storage_get_index" and "storage_put_index", a buffer for merging two strings is allocated with one byte less than the maximum size of the merged strings, causing subsequent function calls to the cfs_open function to read from memory beyond the buffer size. The vulnerability has been patched in the "develop" branch of Contiki-NG, and is expected to be included in the next release. As a workaround, the problem can be fixed by applying the patch in Contiki-NG pull request #2425.