---
id: "CVE-2026-116878"
kind: "vulnerability"
aliases: ["CVE-2026-116878"]
title: "Semantic MediaWiki: anonymous requests can exhaust server CPU, memory, and database connections"
severity: "high"
cvss: 8.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["mediawiki", "package", "php", "self-hosted", "semantic-mediawiki"]
not_affected_if: ["private-wiki-login-required", "version-7.3.1-or-later"]
published_at: "2026-10-27T11:17:29+00:00"
first_seen_at: "2026-10-27T11:31:27+00:00"
updated_at: "2026-10-27T11:31:37+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-116878", "first_seen_at": "2026-10-27T11:31:27+00:00"}]
---

# Semantic MediaWiki: anonymous requests can exhaust server CPU, memory, and database connections

Semantic MediaWiki versions from 2.5.0 before 7.3.1 let anonymous visitors send requests to Special:PropertyLabelSimilarity with limit=0, which removes the SQL limit and forces quadratic string comparisons. Repeated requests can exhaust PHP CPU, memory and database connections, making the wiki unavailable.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Semantic MediaWiki version in the wiki's Special:Version page or in composer.lock for `mediawiki/semantic-media-wiki`
- Confirm whether Special:PropertyLabelSimilarity is reachable without login on the public wiki

## Fix

- Upgrade Semantic MediaWiki to `7.3.1` or later
- Until upgraded, restrict access to Special:PropertyLabelSimilarity at the web server or with MediaWiki access rules (unknown whether the sources list a specific workaround)

## Timeline

- 2026-10-27T11:31:27+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-116878

## From the sources

Semantic MediaWiki from 2.5.0 before 7.3.1 contains an uncontrolled resource consumption vulnerability that allows anonymous attackers to force quadratic computation by supplying a zero limit to Special:PropertyLabelSimilarity. Attackers can send repeated requests with limit=0 to bypass the SQL LIMIT and trigger pairwise similar_text() comparisons, exhausting PHP CPU, memory, and database connections.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_