Eclipse Vert.x: Denial of service via quadratic uniqueItems validation in JSON Schema
Summary
The uniqueItems validation in Eclipse Vert.x (module io.vertx:vertx-json-schema) compares array items pairwise in a quadratic loop without short-circuit or size limit. A remote, unauthenticated attacker can send a moderately sized JSON array that consumes disproportionate CPU time and causes a denial of service. The modules vertx-openapi, vertx-web-validation and vertx-web-openapi-router are also affected because they depend on vertx-json-schema. The impact is limited to availability.
Affected
- Eclipse Vert.x 4.0.0 to 4.5.34
- Eclipse Vert.x 5.0.0 to 5.0.12
- Eclipse Vert.x 5.1.0 to 5.1.9
- Eclipse Vert.x 5.2.0
- Modules: io.vertx:vertx-json-schema, io.vertx:vertx-web-openapi-router, io.vertx:vertx-web-validation, io.vertx:vertx-openapi
- Note: The CVE record and the GHSA list different ranges for 5.1.9, so check the exact version of your module against the advisory.
Fixed in
- vertx-json-schema: 5.2.1, 5.1.10, 4.5.35
- vertx-openapi, vertx-web-validation, vertx-web-openapi-router: 5.2.1, 5.1.9, 4.5.35
- Fixed versions for other 4.x or 5.x branches: Unknown.
Workaround
Unknown. No vendor-documented workaround.
- Own suggestion, not from the vendor: if patching is delayed, limit request body size and array length at the reverse proxy or API gateway, and disable or restrict uniqueItems in affected schemas where the business logic allows it.
Exploitation
- No evidence of exploitation in the wild found.
- No public proof of concept found.
- CISA KEV listing not verified.
- CISA SSVC: Exploitation none, Automatable yes, Technical Impact partial.
Our recommendation
- Inventory Java applications and dependency trees for the listed artifacts, e.g. with an SBOM or mvn dependency:tree.
- Upgrade to the fixed version for the branch in use, after confirming the exact version against the GHSA advisory.
- Check whether JSON validation runs before authentication and whether the API is internet-facing; prioritise these systems.
- Monitor CPU usage and request latency on affected services for signs of abuse.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- GitHub Security Advisory GHSA-4m87-8qfr-8p8m github.com
- Eclipse CVE assignment work item #340 gitlab.eclipse.org
- OpenCVE entry CVE-2026-102461 app.opencve.io
- Vulners NVD record CVE-2026-102461 vulners.com
- OSV record CVE-2026-102461 vulners.com
- Strix CVE record CVE-2026-102461 www.strix.ai
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 02:34.
Original description (NVD)
In Eclipse Vert.x versions [4.0.0, 4.5.34] or [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], the uniqueItems keyword validation uses an O(n²) pairwise comparison loop with no short-circuit or size limit. A remote unauthenticated attacker can submit a moderately-sized JSON array that consumes disproportionate CPU time, leading to denial of service. The impacted component is io.vertx:vertx-json-schema. The following Vert.x modules depend on vertx-json-schema and are also affected: io.vertx:vertx-web-openapi-router io.vertx:vertx-web-validation io.vertx:vertx-openapi
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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