Contiki-NG is an open-source, cross-platform operating system for internet of things devices. It is possible to cause an out-of-bounds write in versions of Contiki-NG prior to 4.6 when transmitting a 6LoWPAN packet with a chain of extension headers. Unfortunately, the written header is not checked to be within the available space, thereby making it possible to write outside the buffer. The problem has been patched in Contiki-NG 4.6. Users can apply the patch for this vulnerability out-of-band as a workaround.