CVE-2013-4570 in MediaWiki
Summary
by MITRE
The zend_inline_hash_func function in php-luasandbox in the Scribuntu extension for MediaWiki before 1.19.10, 1.2x before 1.21.4, and 1.22.x before 1.22.1 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via vectors related to converting Lua data structures to PHP, as demonstrated by passing { [{}] = 1 } to a module function.
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Analysis
by VulDB Data Team • 03/21/2022
The vulnerability identified as CVE-2013-4570 represents a critical denial of service flaw within the php-luasandbox extension component of MediaWiki's Scribuntu extension. This issue specifically targets the zend_inline_hash_func function which serves as a crucial bridge between Lua and PHP data structures during module function execution. The vulnerability manifests when the system attempts to process malformed Lua data structures that contain nested table references, creating a scenario where a NULL pointer dereference occurs during the conversion process from Lua to PHP representation.
The technical exploitation of this vulnerability occurs through carefully crafted input containing nested table structures such as { [{}] = 1 } which when passed to module functions trigger the problematic conversion path. This particular data structure creates a recursive reference pattern that the zend_inline_hash_func function fails to handle properly, resulting in a NULL pointer dereference that ultimately crashes the PHP process. The flaw resides in the insufficient validation and handling of complex nested data structures during the inter-language data conversion process, making it particularly dangerous in web environments where arbitrary user input can be processed.
From an operational perspective, this vulnerability poses significant risk to MediaWiki deployments since it enables remote attackers to execute denial of service attacks without requiring any special privileges or authentication. The crash occurs during normal module function execution, meaning legitimate users could inadvertently trigger the vulnerability through malformed input or malicious actors could exploit it systematically to disrupt service availability. The impact extends beyond simple service interruption as the crash could potentially lead to resource exhaustion or system instability in high-traffic environments where multiple concurrent requests might be processed.
The vulnerability maps to CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations. Additionally, this issue aligns with ATT&CK technique T1499.004 which covers network denial of service attacks through resource exhaustion or system crashes. Organizations using affected MediaWiki versions should prioritize immediate patching to address this vulnerability, as the exposure window remains significant given the widespread adoption of MediaWiki platforms. The recommended mitigation strategy involves upgrading to the patched versions 1.19.10, 1.21.4, and 1.22.1 respectively, while implementing input validation measures to prevent malformed data structures from reaching the vulnerable conversion functions. Organizations should also consider implementing monitoring solutions to detect unusual crash patterns that might indicate exploitation attempts, particularly in environments where the Scribuntu extension is actively used.