CVE-2026-72854 msgpack-c Integer Overflow in msgpack_unpacker_expand_buffer Causes a False-Success Undersized Reservation

msgpackunpackerexpandbuffer in src/unpack.c, reached through the public msgpackunpackerreservebuffer API, computes its new buffer size using an unchecked sizet addition of the requested size and the amount already used. The doubling loop guards its own multiplication against overflow, but the...