Source: msgpack-c Version: 7.0.1-1 X-Debbugs-CC: [email protected] Severity: important Tags: security upstream Forwarded: https://github.com/msgpack/msgpack-c/issues/1181
Hi, The following vulnerability was published for msgpack-c. CVE-2026-72854[0]: | 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.c demonstrates the | reserve-then-write pattern, and its defensive assert comparing | capacity against the request is compiled out under NDEBUG. | msgpack-c's own decode entry points do not derive the reservation | size from untrusted input, so reaching this requires an integration | that passes an attacker-influenced length to the reservation API, | such as a length-prefixed streaming transport. If you fix the vulnerability please also make sure to include the CVE (Common Vulnerabilities & Exposures) id in your changelog entry. For further information see: [0] https://security-tracker.debian.org/tracker/CVE-2026-72854 https://www.cve.org/CVERecord?id=CVE-2026-72854 [1] https://github.com/msgpack/msgpack-c/issues/1181 [2] https://github.com/msgpack/msgpack-c/commit/8a48af0e3ed15ce0e60273de30a073ae6419489e Please adjust the affected versions in the BTS as needed. Regards, Salvatore
