# CVE-2026-126565: Semantic MediaWiki denial of service in concept expansion

Source: https://junglewise.ai/threats/cve-2026-126565-semantic-mediawiki-3-0-0-before-7-4-1-contains-a-denial-of  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-11. Updated: 2026-11-11  
License: CC BY 4.0 with a link back

CVE-2026-126565 · Severity: medium · CVSS 4.3 · Published 2026-11-11

Semantic MediaWiki, a structured data extension for MediaWiki wiki software, contains a denial of service flaw in its query engine. An attacker with page-edit rights can create chains of concept pages that cause queries to exhaust server CPU and memory, disrupting wiki availability. The vulnerability affects both ElasticStore and SPARQLStore query backends.

Technologies: [Semantic MediaWiki](https://junglewise.ai/threats/technologies/semantic-mediawiki). Vendors: [Semantic MediaWiki](https://junglewise.ai/threats/vendors/semantic-mediawiki).

## Quick answers

**Is CVE-2026-126565 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-126565 being exploited in the wild.

**How severe is CVE-2026-126565?** Medium severity, with a CVSS score of 4.3, published 11 November 2026.

**Which products and versions are affected?** Semantic MediaWiki 3.0.0 before 7.4.1.

**Is there a fix for CVE-2026-126565?** Yes: fixed in Semantic MediaWiki 7.4.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-126565 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-126565?** Check whether you run Semantic MediaWiki at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Semantic MediaWiki 7.4.1

## Technical details

The ConceptDescriptionInterpreter classes in ElasticStore and SPARQLStore recursively expand concept definitions without memoization, caching, or an expansion budget limit. An attacker with edit permissions can construct acyclic concept chains that fan out exponentially, causing concept queries via page views, Special:Ask queries, or api.php action=ask requests to consume unbounded CPU and memory resources until the server becomes unresponsive.

## Affected products

- Semantic MediaWiki Semantic MediaWiki 3.0.0 before 7.4.1

## Timeline

- 2026-11-11: disclosed

## References

- [https://github.com/SemanticMediaWiki/SemanticMediaWiki/blob/7.4.0/src/Elastic/QueryEngine/DescriptionInterpreters/ConceptDescriptionInterpreter.php](https://github.com/SemanticMediaWiki/SemanticMediaWiki/blob/7.4.0/src/Elastic/QueryEngine/DescriptionInterpreters/ConceptDescriptionInterpreter.php)
- [https://github.com/SemanticMediaWiki/SemanticMediaWiki/blob/7.4.0/src/SPARQLStore/QueryEngine/DescriptionInterpreters/ConceptDescriptionInterpreter.php](https://github.com/SemanticMediaWiki/SemanticMediaWiki/blob/7.4.0/src/SPARQLStore/QueryEngine/DescriptionInterpreters/ConceptDescriptionInterpreter.php)

## Related threats

- [Semantic MediaWiki authorization bypass in edit protection](https://junglewise.ai/threats/cve-2026-126566-semantic-mediawiki-7-3-1-before-7-4-1-contains-an-incorrect)
- [Semantic MediaWiki stored XSS in ValueFormatter property label](https://junglewise.ai/threats/cve-2026-126564-semantic-mediawiki-2-5-0-before-7-4-1-contains-a-stored-cross)
- [Semantic MediaWiki uncontrolled recursion in ConceptDescriptionInterpreter](https://junglewise.ai/threats/cve-2026-126562-semantic-mediawiki-3-0-0-before-7-4-1-contains-an-uncontrolled)
- [Semantic MediaWiki missing authorization in page edit protection](https://junglewise.ai/threats/cve-2026-126561-semantic-mediawiki-2-5-0-before-7-4-1-contains-a-missing)
- [Semantic MediaWiki stored cross-site scripting in DataTables](https://junglewise.ai/threats/cve-2026-126560-semantic-mediawiki-3-0-0-before-7-4-1-contains-a-stored-cross)