Threat database

MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.3, the msgpack-python C extension (msgpack._cmsgpack) leaks a decoded map value when deserialization rejects a key with strict_map_key=True (the default). Repeated malformed inputs can cause unbounded process memory growth and denial of service in applications that deserialize attacker-controlled MessagePack data. Both unpackb() and the streaming Unpacker API are affected. The pure-Python fallback does not exhibit this leak in the reported tests. This issue is fixed in version 1.2.3.

msgpack-java versions up to 0.9.12 contain an integer overflow vulnerability in the MessageUnpacker.skipValue() method. This occurs when processing MAP32 containers with very large element counts, specifically at or above 0x40000000. The overflow causes the parser cursor to desynchronize, potentially resulting in attacker-controlled data being returned instead of expected fields. The vulnerability has a medium severity with a CVSS score of 6.9.

CVE-2026-90472 is a stack overflow vulnerability in msgpack-java versions up to 0.9.12. It occurs in the MessageUnpacker.unpackValue() method, which recursively deserializes arrays and maps without limiting nesting depth. Crafted payloads with deeply nested arrays can cause a StackOverflowError, leading to deserialization failures during request processing.

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.

MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.2, MessagePack::Buffer#clear in ext/msgpack/buffer.c leaves rmem_last, rmem_end, and rmem_owner stale after _msgpack_buffer_shift_chunk returns an rmem page to the shared pool, allowing a subsequent Buffer#write and a second MessagePack::Buffer to alias the page and disclose or corrupt cross-buffer data. This issue is fixed in version 1.8.2.

MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.1, there is an Out-of-bounds read/crash on Unpacker reuse after a caught error, potentially leading to a DoS attack. If the Unpacker is used repeatedly after an error occurs, the process may crash with a SEGV. This issue has been fixed in version 1.2.1.

CVE-2026-21452 is a high-severity denial-of-service vulnerability in msgpack-java versions prior to 0.9.11. It arises from uncontrolled resource consumption during deserialization of maliciously crafted . msgpack files containing EXT32 objects with attacker-controlled payload lengths. The vulnerability allows remote attackers to cause JVM heap exhaustion and service crashes without requiring authentication or user interaction. This can disrupt applications that deserialize untrusted . msgpack files, such as model registries, inference services, and CI/CD pipelines. The exploit involves a small but valid . msgpack file that bypasses basic validation and triggers unbounded memory allocation.

EPSS 0.6%Vulnerabilitymsgpack#cwe-400#cwe-789Germany+9