CVE-2019-16228 in py-lmdb
Summary
by MITRE
An issue was discovered in py-lmdb 0.97. There is a divide-by-zero error in the function mdb_env_open2 if mdb_env_read_header obtains a zero value for a certain size field.
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Analysis
by VulDB Data Team • 12/19/2023
The vulnerability identified as CVE-2019-16228 represents a critical divide-by-zero error within the py-lmdb library version 0.97, specifically manifesting in the mdb_env_open2 function when mdb_env_read_header encounters a zero value in a crucial size field. This flaw exists within the Lightweight Memory-Mapped Database (LMDB) implementation that py-lmdb provides as a Python interface, creating a potential denial-of-service condition that could be exploited by malicious actors. The issue stems from inadequate input validation mechanisms within the database header parsing routine, where the system fails to properly validate size parameters before performing arithmetic operations.
The technical execution of this vulnerability occurs when the mdb_env_read_header function processes a malformed database file or header structure that contains a zero value in a size field that is subsequently used as a divisor in arithmetic operations within mdb_env_open2. This type of error falls under the CWE-369 vulnerability category, which specifically addresses divide-by-zero conditions that can lead to system instability or crashes. The flaw demonstrates poor error handling practices where the system does not properly validate input data before utilizing it in mathematical computations, creating a path for exploitation that can result in complete application termination or system unresponsiveness.
From an operational perspective, this vulnerability poses significant risks to applications that rely on py-lmdb for data storage and retrieval operations. The divide-by-zero condition can cause immediate application crashes, leading to denial-of-service scenarios that disrupt legitimate user access and potentially expose underlying system resources to further exploitation attempts. Attackers could leverage this vulnerability by crafting malicious database files or manipulating existing database structures to trigger the error condition, effectively creating a reliable method for causing system downtime. The impact extends beyond simple service disruption as it may also provide a foothold for more sophisticated attacks that could exploit the resulting system instability.
Security practitioners should implement immediate mitigations including upgrading to py-lmdb versions that contain patches addressing this divide-by-zero condition, typically those released after the vulnerability disclosure. Organizations should also consider implementing input validation controls and monitoring for anomalous database access patterns that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1499.004, which covers network disruption through resource exhaustion or system instability, and represents a classic example of how seemingly minor input validation flaws can result in significant operational impacts. Additionally, implementing proper error handling and defensive programming practices within database interface libraries can prevent similar issues from occurring in other components of the application stack.