CVE-2019-16225 in py-lmdb
Summary
by MITRE
An issue was discovered in py-lmdb 0.97. For certain values of mp_flags, mdb_page_touch does not properly set up mc->mc_pg[mc->top], leading to an invalid write operation.
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Analysis
by VulDB Data Team • 12/19/2023
The vulnerability identified as CVE-2019-16225 resides within the py-lmdb library version 0.97, which is a Python interface to the Lightning Memory-Mapped Database system. This flaw represents a critical memory corruption issue that can potentially lead to arbitrary code execution or system instability. The vulnerability manifests specifically when handling certain mp_flags values during database page operations, creating a scenario where memory management becomes compromised. The issue stems from improper handling of page touch operations within the database's memory mapping subsystem, which is fundamental to how LMDB manages its data structures and memory allocation patterns.
The technical root cause of this vulnerability lies in the mdb_page_touch function's failure to correctly initialize the mc->mc_pg[mc->top] pointer when specific memory flags are processed. This improper initialization creates a condition where subsequent memory operations attempt to write to an uninitialized or improperly allocated memory location. The flaw occurs during the page touch operation which is responsible for updating memory-mapped pages and their associated metadata structures. When the mp_flags parameter contains certain combinations of memory management flags, the function fails to properly set up the page pointer array, leading to a dangling pointer scenario. This misconfiguration results in an invalid write operation that can overwrite adjacent memory regions or corrupt critical data structures within the database's memory space.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can enable attackers to manipulate the database's internal state through carefully crafted inputs. When exploited, this vulnerability could allow an attacker to achieve arbitrary code execution within the context of the application using py-lmdb, potentially leading to complete system compromise. The vulnerability is particularly concerning because it operates at a low level within the database engine's memory management system, making it difficult to detect through standard application-level security measures. The invalid write operation can corrupt critical database structures such as page headers, transaction metadata, or other internal data structures that maintain the integrity of the database system. This type of vulnerability aligns with CWE-787: "Out-of-bounds Write" and represents a classic memory safety issue that can be exploited through buffer overflow techniques.
From an attack perspective, this vulnerability falls under the ATT&CK framework's technique T1059.007 for "Command and Scripting Interpreter: Python" and T1068 for "Exploitation for Privilege Escalation" when the database application runs with elevated privileges. The exploitation requires an attacker to control the mp_flags parameter passed to the database operations, which could occur through injection attacks, malformed data processing, or other input manipulation techniques. The vulnerability demonstrates a weakness in the memory management layer of the database system, specifically in how it handles page touch operations under specific memory flag conditions. Security researchers have identified that this flaw could be leveraged to bypass security controls, corrupt database content, or potentially gain unauthorized access to sensitive information stored within the database. The impact is particularly severe in environments where py-lmdb is used for critical data storage and where the application has elevated privileges.
Mitigation strategies for CVE-2019-16225 should focus on immediate patching of the py-lmdb library to version 0.98 or later, which contains the necessary fixes for the memory management issue. Organizations should implement input validation and sanitization measures to prevent malicious mp_flags values from reaching the vulnerable code paths, particularly in applications that process untrusted data through the database interface. Additionally, monitoring systems should be enhanced to detect anomalous database behavior patterns that might indicate exploitation attempts. The fix implemented in newer versions addresses the core memory initialization issue by ensuring proper setup of mc->mc_pg[mc->top] before any write operations occur. Security teams should also consider implementing runtime protections such as address space layout randomization, stack canaries, and memory protection mechanisms to reduce the exploitability of similar vulnerabilities in the broader system landscape.