CVE-2015-2352 in MyBB
Summary
by MITRE
The cache handler in MyBB (aka MyBulletinBoard) before 1.8.4 does not properly check the encoding of input to the var_export function, which allows attackers to have an unspecified impact via unknown vectors.
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Analysis
by VulDB Data Team • 01/10/2018
The vulnerability identified as CVE-2015-2352 affects MyBB versions prior to 1.8.4 and resides within the cache handler component of the bulletin board software. This flaw specifically relates to improper input validation when processing data through the var_export function, which is a PHP built-in function used for generating code representations of variables. The cache handler in MyBB is responsible for storing and retrieving cached data to improve performance, making it a critical component that requires robust security controls. When the system fails to properly validate the encoding of input data before passing it to var_export, it creates an avenue for potentially malicious input to be processed in unexpected ways.
The technical nature of this vulnerability stems from the lack of proper sanitization and validation of user-supplied data within the cache handling mechanism. The var_export function in PHP can generate PHP code representations of variables, and when this function receives unvalidated input, it can produce malformed output that may be executed or interpreted in unintended ways. This type of vulnerability falls under the category of improper input validation and can be classified as CWE-20, which represents "Improper Input Validation" in the Common Weakness Enumeration catalog. The vulnerability allows attackers to potentially manipulate the cache system in ways that could lead to arbitrary code execution or data corruption, though the exact attack vectors remain unspecified in the CVE description.
The operational impact of this vulnerability extends beyond simple data integrity concerns, as it could enable attackers to manipulate the caching system to achieve unauthorized access or execution of malicious code. In bulletin board systems like MyBB, where user-generated content is prevalent, the cache handler becomes a potential attack surface for privilege escalation or persistent malicious activities. The unspecified impact mentioned in the CVE description suggests that the vulnerability could potentially lead to multiple attack scenarios including but not limited to code injection, data manipulation, or denial of service conditions. This vulnerability particularly affects web applications that rely heavily on caching mechanisms for performance optimization, as demonstrated by the MyBB platform's architecture.
Mitigation strategies for CVE-2015-2352 should focus on implementing proper input validation and sanitization before any data is processed by the var_export function or similar PHP functions that can generate executable code representations. Organizations should immediately upgrade to MyBB version 1.8.4 or later, which contains the necessary patches to address this vulnerability. Additional defensive measures include implementing proper encoding validation, using parameterized inputs where possible, and establishing robust input filtering mechanisms that prevent malicious payloads from reaching the cache handler. The mitigation approach aligns with ATT&CK technique T1059.006 for "Command and Scripting Interpreter: PowerShell" and broader defensive practices outlined in the MITRE ATT&CK framework for preventing code injection vulnerabilities. Regular security audits of caching mechanisms and input validation routines should be conducted to prevent similar issues from emerging in other components of the application stack.