CVE-2012-4885 in MediaWiki
Summary
by MITRE
The wikitext parser in MediaWiki 1.17.x before 1.17.3 and 1.18.x before 1.18.2 allows remote attackers to cause a denial of service (infinite loop) via certain input, as demonstrated by the padleft function.
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Analysis
by VulDB Data Team • 12/13/2021
The vulnerability identified as CVE-2012-4885 represents a critical denial of service flaw within the wikitext parser component of MediaWiki software. This issue affects versions 1.17.x prior to 1.17.3 and 1.18.x prior to 1.18.2, creating a significant security risk for organizations relying on MediaWiki platforms for content management. The vulnerability specifically targets the parser's handling of certain input sequences that trigger infinite loop conditions during processing. The attack vector is particularly concerning as it enables remote exploitation without requiring authentication, making it accessible to any attacker with network access to the affected system. The demonstration of this vulnerability through the padleft function highlights the parser's susceptibility to malformed input that can cause recursive processing behaviors leading to system resource exhaustion.
The technical implementation of this vulnerability stems from inadequate input validation and boundary checking within the wikitext parsing logic. When the parser encounters specific combinations of characters or formatting elements, particularly those related to the padleft function, it enters into a recursive processing loop that consumes excessive CPU cycles and memory resources. This infinite loop condition prevents the parser from completing its processing tasks and effectively renders the affected MediaWiki instance unavailable to legitimate users. The flaw operates at the parser level rather than at the application layer, making it particularly difficult to detect and mitigate through traditional network-based security measures. According to CWE classification, this vulnerability maps to CWE-835, which specifically addresses the issue of infinite loops in software implementations where a loop lacks proper termination conditions or fails to properly validate input parameters that could cause iterative processes to continue indefinitely.
The operational impact of CVE-2012-4885 extends beyond simple service disruption to potentially compromise the overall availability and reliability of MediaWiki-based platforms. Organizations using affected versions may experience complete service outages during attack periods, leading to significant business disruption and potential loss of user confidence. The vulnerability's remote nature means that attackers can exploit it from anywhere on the internet without requiring physical access or insider knowledge of the system. This characteristic aligns with ATT&CK technique T1499.004, which describes network denial of service attacks that target availability through resource exhaustion. The infinite loop condition can cause system processes to consume 100% CPU utilization, potentially leading to cascading failures across dependent services and applications that rely on the affected MediaWiki installation.
Mitigation strategies for this vulnerability primarily focus on immediate version upgrades to patched releases of MediaWiki software. Organizations should prioritize upgrading to MediaWiki 1.17.3 or 1.18.2, which contain the necessary fixes to prevent the infinite loop conditions in the wikitext parser. Additionally, implementing input validation measures at the network level can provide temporary protection while upgrades are being deployed. Security administrators should consider implementing rate limiting and resource monitoring to detect unusual processing patterns that may indicate exploitation attempts. The fix implemented in the patched versions typically involves enhanced boundary checking and input sanitization within the parser's handling of formatting functions, particularly those related to text alignment and padding operations. Organizations should also conduct thorough testing of their MediaWiki installations to ensure that all affected versions have been properly updated and that no legacy configurations remain that could still be vulnerable to similar attacks.