diff3 tool from GNU diffutils is vulnerable to a heap‑based buffer overflow due to multiple signed integer overflows in line‑mapping calculations. Incorrect arithmetic in mapping line ranges can result in corrupted values being used for memory allocation and loop bounds. When processing crafted diff output, these overflows may cause the application to allocate insufficient memory and subsequently perform out‑of‑bounds writes during internal processing.  An attacker who can control the output of the diff program used by diff3 (e.g. via --diff-program pointing to a malicious script) can trigger out-of-bounds writes, resulting in a crash and potentially remote code execution depending on the environment.

This issue has been fixed in commit 9ff04d5b84743e331e80b589335a52c5480d1815

NOTE: The project maintainers claim that this is not a security issue. They state that the worst outcome this issue can cause is a crash of diff and that it cannot be used to escalate privileges.