Vert.x MySQL client: Denial of service via uncapped column count
Summary
The vertx-mysql-client module of Eclipse Vert.x pre-allocates an array for column definitions based on the column count declared by the MySQL server, without an upper limit. A malicious or compromised MySQL server, or an attacker in a man-in-the-middle position on the database connection, can send a crafted result set that triggers a massive heap allocation. The resulting OutOfMemoryError crashes the Netty event loop thread, which stops all connections and verticles of the application (denial of service).
Affected
- Eclipse Vert.x 4.0.0 to 4.5.34 (vertx-mysql-client)
- Eclipse Vert.x 5.0.0 to 5.0.12 (per CVE record; the GHSA lists no fix for 5.0.x)
- Eclipse Vert.x 5.1.0 to 5.1.9 (GHSA lists up to 5.1.8)
- Eclipse Vert.x 5.2.0 (per CVE record; GHSA lists 5.2.0 as affected)
Fixed in
- 4.5.35
- 5.1.10
- 5.2.1
- 5.0.x: Unknown. No fixed 5.0.x release was found in the sources.
Workaround
- No vendor-documented workaround. Upgrading to a patched version is the only documented remedy.
Exploitation
- No evidence of exploitation in the wild found. CISA SSVC: exploitation none, automatable no.
- No public proof of concept found at the time of research.
Our recommendation
- Check whether any application uses io.vertx:vertx-mysql-client (including bundled third-party products) and identify the exact version.
- Upgrade to 4.5.35, 5.1.10 or 5.2.1. For 5.0.x, verify the fix with the Vert.x maintainers before relying on an upgrade path.
- Until patched, connect only to MySQL servers you control, over trusted networks, using TLS.
- Monitor Vert.x services for unexpected crashes or restarts.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- GitHub Security Advisory GHSA-9jxp-x3fr-ffqh github.com
- Eclipse CVE assignment work item #342 gitlab.eclipse.org
- OSV record CVE-2026-102466 osv.dev
- NVD record via Vulners vulners.com
- VulDB entry 420551 vuldb.com
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, 16:05.
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 Vert.x MySQL client (vertx-mysql-client) pre-allocates an array for column definitions based on a server-declared column count with no upper-bound validation. A malicious or compromised MySQL server, or an attacker with man-in-the-middle positioning, can send a crafted result set packet with an extremely large column count, causing the client to attempt a massive heap allocation. The resulting OutOfMemoryError crashes the Netty event loop thread, causing a complete denial of service for all connections and verticles in the Vert.x application. The impacted component is io.vertx:vertx-mysql-client.
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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