CVE-2016-9036 in Msgpuck Library
Summary
by MITRE
An exploitable incorrect return value vulnerability exists in the mp_check function of Tarantool's Msgpuck library 1.0.3. A specially crafted packet can cause the mp_check function to incorrectly return success when trying to check if decoding a map16 packet will read outside the bounds of a buffer, resulting in a denial of service vulnerability.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/12/2022
The vulnerability identified as CVE-2016-9036 represents a critical flaw in Tarantool's Msgpuck library version 1.0.3 that demonstrates a classic buffer overread condition through incorrect return value handling. This issue specifically affects the mp_check function which is responsible for validating messagepack data structures during parsing operations. The vulnerability arises from a fundamental logic error where the function fails to properly validate buffer boundaries when processing map16 packets, which are 16-bit map structures in the messagepack binary serialization format. When maliciously crafted packets are processed, the mp_check function incorrectly reports successful validation even when the packet structure would cause the parser to read beyond the allocated buffer limits, creating a scenario where memory access violations could occur.
The technical implementation of this vulnerability stems from improper boundary checking within the mp_check function's validation logic. Messagepack format supports various data types including maps, and map16 specifically refers to a 16-bit encoded map structure that contains a specific number of key-value pairs. The flaw occurs when the function attempts to verify whether decoding such a structure would result in reading beyond the buffer's allocated memory space. Due to incorrect conditional logic or missing boundary checks, the function returns a success code even when the calculated read operations would exceed buffer boundaries. This incorrect return value propagates through the parsing stack, allowing malformed data to be processed as valid input, which can lead to unpredictable behavior including memory corruption or application crashes.
From an operational impact perspective, this vulnerability creates a significant denial of service risk for systems utilizing Tarantool's Msgpuck library for data serialization and deserialization. The vulnerability can be exploited by sending specially crafted packets to any application that relies on this library for processing messagepack formatted data, potentially affecting database operations, network services, or any system component that handles messagepack communication. The nature of the flaw means that even a single malicious packet could cause the affected application to crash or become unresponsive, effectively denying service to legitimate users. This vulnerability is particularly concerning in high-availability systems where such disruptions could have cascading effects across dependent services, and the impact extends beyond simple application crashes to potentially compromise system stability and data integrity.
The vulnerability aligns with CWE-129: Improper Validation of Array Index, which specifically addresses issues where array or buffer indices are not properly validated before use, and can be categorized under ATT&CK technique T1499.004: Endpoint Denial of Service. The flaw demonstrates poor input validation practices and highlights the critical importance of proper buffer boundary checking in serialization libraries. Organizations should implement immediate mitigations including updating to patched versions of Tarantool's Msgpuck library, implementing input validation at application layers, and deploying network monitoring to detect and block malformed messagepack packets. Additionally, defensive programming practices such as implementing comprehensive boundary checks, using memory-safe programming languages or libraries, and conducting regular security audits of serialization components should be prioritized to prevent similar vulnerabilities from emerging in other software components. The incident underscores the necessity of rigorous testing for buffer overflow conditions and proper return value validation in security-critical libraries that handle external data input.