Eclipse Wakaama CoAP Block1 Handler Unbounded Memory Allocation DoS

Eclipse Wakaama before snapshot/2026-05-26 contains an unbounded memory allocation vulnerability in the CoAP Block1 handler within coap/block.c that allows unauthenticated remote attackers to exhaust server memory by sending a sequence of Block1 PUT requests with incrementing block numbers. Attackers can target the registration endpoint over UDP without authentication, causing the server to repeatedly reallocate a growing accumulation buffer by appending each block payload without enforcing any maximum total size limit, resulting in denial of service through memory exhaustion.

In Eclipse Wakaama, ever since its inception until 2021-01-14, the CoAP parsing code does not properly sanitize network-received data.

In Eclipse Wakaama (formerly liblwm2m) 1.0, core/er-coap-13/er-coap-13.c in lwm2mserver in the LWM2M server mishandles invalid options, leading to a memory leak. Processing of a single crafted packet leads to leaking (wasting) 24 bytes of memory. This can lead to termination of the LWM2M server after exhausting all available memory.