CVE-2026-116871 in Semantic MediaWiki
Summary
by MITRE • 10/27/2026
Semantic MediaWiki 3.0.0 before 7.3.1 contains an uncontrolled recursion vulnerability in LegacyParser::getSubqueryDescription() that processes nested query tokens before depth limits apply. Unauthenticated attackers can submit deeply nested query elements to the action=ask API to consume substantial CPU and memory, tying up request workers.
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Analysis
by VulDB Data Team • 10/27/2026
The identified vulnerability resides within Semantic MediaWiki versions prior to 7.3.1, specifically affecting the LegacyParser::getSubqueryDescription() function which is responsible for processing nested query tokens in semantic queries. This component handles complex data retrieval operations where users can define intricate relationships between wiki pages using structured syntax. The core technical flaw involves a failure to enforce depth limits on recursive calls before they are executed, allowing an attacker to construct deeply nested query structures that trigger uncontrolled recursion within the parser logic. When such malformed or excessively deep queries are submitted via the action=ask API endpoint, the system attempts to resolve each level of nesting sequentially without adequate safeguards against infinite loops or excessive stack depth.
From a technical perspective, this represents a classic case of improper input validation leading to resource exhaustion. The uncontrolled recursion allows an attacker to consume substantial amounts of CPU and memory resources on the server side as the application struggles to parse and evaluate the deeply nested logical structures. This behavior ties up request workers effectively creating a denial-of-service condition for legitimate users who rely on the wiki platform for information retrieval or collaboration. Since the vulnerability can be exploited by unauthenticated attackers, it poses a significant risk even in environments where user registration is restricted or not required for basic viewing and querying operations.
The operational impact of this vulnerability extends beyond simple service disruption. By consuming server resources through recursive processing attacks, adversaries can degrade overall system performance, potentially causing timeouts for other critical applications hosted on the same infrastructure. In high-traffic wiki deployments, such resource contention can lead to cascading failures where multiple concurrent attack requests amplify the strain on backend services. This aligns with common threat models involving application-layer denial-of-service attacks that target specific logic flaws rather than network bandwidth saturation.
Industry standards classify this type of flaw under CWE-675 which denotes use of outdated or weak cryptographic algorithms, but more accurately it falls under CWE-400 concerning uncontrolled resource consumption due to recursion depth issues. In the context of MITRE ATT&CK framework, this vulnerability facilitates techniques associated with Resource Hijacking and Denial of Service via application layer exploitation. Attackers leverage these weaknesses to disrupt availability without needing elevated privileges or prior authentication credentials.
Mitigation strategies should prioritize immediate patching to version 7.3.1 or later where the recursion depth limits are properly enforced before query processing begins. Administrators must ensure that all instances of Semantic MediaWiki within their ecosystem are updated consistently to prevent exploitation across different nodes in a distributed environment. Additionally, implementing web application firewalls with rules capable of detecting and blocking excessively deep nested structures can provide an additional layer of defense against such recursive attacks while patches are being deployed. Monitoring server metrics for unusual spikes in CPU usage associated with wiki query endpoints may also aid in early detection of ongoing exploitation attempts.