Vulnerabilities & PatchesEmerging1 src
CVE-2026-72854 - msgpack-c Integer Overflow in msgpack_unpacker_expand_buffer Causes a False-Success Undersized Reservation
CVE ID : CVE-2026-72854
Published : Aug. 20, 2026, 6:19 p. m.
• 50 minutes ago
Description : msgpack_unpacker_expand_buffer in src/unpack. c, reached through the public msgpack_unpacker_reserve_buffer API, computes its new buffer size using an unchecked size_t addition of the requested size and the amount already used.
The doubling loop guards its own multiplication against overflow, but the addition in the loop condition is unguarded, so a request near SIZE_MAX wraps: the loop condition is already satisfied, the allocation is performed at the small pre-wrap size, and the function returns true.
The caller is told the requested capacity was reserved when it was not, so a subsequent write of the requested length overflows the heap buffer. The library's own example/lib_buffer_unpack.
