CryptoLib provides a software-only solution using the CCSDS Space Data Link Security Protocol - Extended Procedures (SDLS-EP) to secure communications between a spacecraft running the core Flight System (cFS) and a ground station. In 1.3.3 and earlier, a heap buffer overflow vulnerability persists in the Crypto_TC_ApplySecurity function due to an incomplete validation check on the fl (frame length) field. Although CVE-2025-29912 addressed an underflow issue involving fl, the patch fails to fully prevent unsafe calculations. As a result, an attacker can still craft malicious frames that cause a negative tf_payload_len, which is then interpreted as a large unsigned value, leading to a heap buffer overflow in a memcpy call.
The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.