Key points
- Eclipse Vert.x versions through 4.5.34, 5.0.12, 5.1.9 and 5.2.0 are affected.
- The vulnerability is rated HIGH with a CVSS score of 8.2.
- No fix has been confirmed as available in the source material provided.
Eclipse Vert.x applications using the MSSQL client component face a high-severity vulnerability that allows remote servers to crash client systems. The flaw affects versions 4.0.0 through 4.5.34, 5.0.0 through 5.0.12, 5.1.0 through 5.1.9, and version 5.2.0. Teams relying on this library for database connectivity should verify their current version immediately.
In plain English
The issue lies in how the client handles incoming data from SQL servers. When receiving messages, the software combines data packets into a single buffer in direct memory. According to the National Vulnerability Database record for CVE-2026-102462, this process lacks a cumulative size limit. A server can send a continuous stream of packets without signaling the end of the message, forcing the client to keep allocating memory until it runs out.
The background
This out-of-memory condition occurs before the client completes authentication. This means an attacker does not need valid credentials to exploit the flaw. The source material notes that a malicious, compromised, or man-in-the-middle SQL server can trigger this behavior. The affected component is specifically the io.vertx:vertx-mssql-client library within the Eclipse Vert.x framework.
What changes now
Organizations using these specific version ranges of the MSSQL client are exposed to denial-of-service risks. Since the crash happens before authentication, any server the client connects to can potentially trigger the failure. Users must determine if their applications utilize the vertx-mssql-client module. If they do, they fall within the scope of this vulnerability.
Who needs to act first
Teams should prioritize updating systems that expose the MSSQL client to untrusted or public SQL servers. Infrastructure teams usually start by isolating these connections behind strict network controls to limit exposure while waiting for updates. Security engineers should back up configurations and test any potential patches in a staging environment before rolling them out to production. Monitoring for unexpected memory spikes can help detect exploitation attempts early.
What to do and how to stay safe: Eclipse Vert.x
- Inventory all applications using the io.vertx:vertx-mssql-client library to confirm version numbers.
- Restrict network access to ensure clients only connect to trusted, internal SQL servers.
- Monitor client memory usage for unusual spikes that indicate unbounded allocation.
- Watch for vendor announcements regarding a security update for affected versions.
Step-by-step guide: Emergency Patching: How to Fix Critical Flaws Without Breaking Systems
General security guidance from the Patch Review newsroom. It is not confirmed advice from the organisations named in this story.
Frequently asked questions
What is the severity rating for CVE-2026-102462?
The flaw is rated HIGH with a CVSS score of 8.2.
Does this vulnerability require authentication to exploit?
No, the out-of-memory crash occurs before authentication completes.
Which specific versions of Eclipse Vert.x are affected?
Versions 4.0.0 through 4.5.34, 5.0.0 through 5.0.12, 5.1.0 through 5.1.9, and 5.2.0 are impacted.
