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CVE-2026-6860 — vertx-core

Fix: eclipse-vertx/vert.x#6102

CVE-2026-6860 is a CWE-770 vulnerability in io.vertx:vertx-core. A fix is available for io.vertx:vertx-core — see the affected versions and patch details below.

Vert.x has a DoS via unbounded server-side SNI SslContext cache growth

Also known asGHSA-3g76-f9xq-8vp6
Published
Updated
Affected
4 pkgs
Patched
2 / 4
Exploits
None indexed
Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-6860.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs15th percentile — riskier than 15% of all scored CVEsHighest risk
0.00%0.27%0.54%0.81%0.0%0.2%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

4 pkgs affected
☕io.vertx:vertx-core☕io.vertx:vertx-core☕io.vertx:vertx-core☕io.vertx:vertx-core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Potential unbounded server-side SNI SslContext cache growth in Vert.x TLS handling, with = resource-exhaustion / DoS impact. On affected versions, matching server-side SNI names are cached via computeIfAbsent(serverName, ...) in a serverName-keyed SslContext cache.

The implementation differs slightly by branch, but the same sink appears to be present in released versions 4.3.4 through 5.0.11:

  • 4.3.x: SSLHelper
  • 4.4.x / 4.5.x: SslChannelProvider
  • 5.0.x and current master: SslContextProvider

When server-side SNI is enabled and wildcard or otherwise broad hostname mappings are used, an unauthenticated client can send many distinct matching SNI names and cause the server to retain increasing numbers of SslContext entries over time, leading to increasing memory consumption and possible DoS conditions.

Steps to reproduce

  1. Configure a Vert.x server with setSsl(true) and setSni(true).
  2. Use a keystore or mapping where many distinct SNI names match a wildcard or similarly broad rule.
  3. Send repeated connections with distinct matching SNI values.
  4. Observe that the SNI cache size grows with the number of unique matching names.

What are the affected versions?

Affected released versions confirmed on origin:

  • 4.3.4 through 4.3.8
  • 4.4.0 through 4.4.9
  • 4.5.0 through 4.5.26
  • 5.0.0 through 5.0.11

Not affected by the same sink:

  • 4.0.x through 4.2.x
  • 4.3.0 through 4.3.3

Affected Packages

4 total 2 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenio.vertx:vertx-core≥ 4.3.4No fix
☕Mavenio.vertx:vertx-core≥ 4.4.0No fix
☕Mavenio.vertx:vertx-core≥ 4.5.0&&< 4.5.274.5.27io.vertx:vertx-core:4.5.27
☕Mavenio.vertx:vertx-core≥ 5.0.0&&< 5.0.125.0.12io.vertx:vertx-core:5.0.12

Affected Products

1 product · 2 configurations
Application
vert.xeclipse
≥ 5.0.0 && ≤ 5.0.11
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.vertx:vertx-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    A fix is available for CVE-2026-6860; check the affected-versions list above or the advisory for the patched release of io.vertx:vertx-core, then make sure no transitive dependency still pins the vulnerable range.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

This flaw is rated as Moderate because a remote attacker can trigger a denial of service in Red Hat products that use `eclipse-vertx/vert.x` and are configured with TLS wildcard server names. Exploitation occurs during the TLS handshake, impacting service availability without affecting data confidentiality or…

Workaround published by Red Hat
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Source: Red Hat security advisory for CVE-2026-6860 (CC BY 4.0)
ProductFixed inAdvisory
Cryostat 4 on RHEL 9cryostat/cryostat-reports-rhel9:4.2.0-13RHSA-2026:48151
Red Hat build of Apache Camel 4.18.3 for Spring Boot 3.5.16vertx-coreRHSA-2026:54622
Red Hat build of Keycloak 26.4rhbk/keycloak-operator-bundle:26.4.13-1RHSA-2026:30050
Red Hat build of Keycloak 26.4.13rhbk/keycloak-rhel9RHSA-2026:30049
Red Hat build of Keycloak 26.6rhbk/keycloak-operator-bundle:26.6.4-2RHSA-2026:30084
Red Hat build of Keycloak 26.6.4rhbk/keycloak-rhel9RHSA-2026:30083
Red Hat build of Quarkus 3.27.4.SP1io.vertx/vertx-core:4.5.28.redhat-00001RHSA-2026:26018
Red Hat build of Quarkus 3.33.2.SP1io.vertx/vertx-core:4.5.28.redhat-00001RHSA-2026:26017

Frequently Asked Questions

Potential unbounded server-side SNI `SslContext` cache growth in Vert.x TLS handling, with = resource-exhaustion / DoS impact. On affected versions, matching server-side SNI names are cached via `computeIfAbsent(serverName, ...)` in a serverName-keyed `SslContext` cache. The implementation differs slightly by branch, but the same sink appears to be present in released versions `4.3.4` through `5.0.11`: - `4.3.x`: `SSLHelper` - `4.4.x` / `4.5.x`: `SslChannelProvider` - `5.0.x` and current `master`: `SslContextProvider` When server-side SNI is enabled and wildcard or otherwise broad hostname m
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CVE-2026-6860: vertx-core DoS — Fixed in 4.5.27