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MEDIUM severity

GHSA-3g76-f9xq-8vp6 — vertx-core

MEDIUMFix: eclipse-vertx/vert.x#6102

GHSA-3g76-f9xq-8vp6 is a medium-severity (CVSS 5.3) 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 asCVE-2026-6860
Published
May 9, 2026
Updated
Sep 10, 2026
Affected
4 pkgs
Patched
2 / 4
Exploits
None indexed
Exploitation data as of Sep 20, 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 GHSA-3g76-f9xq-8vp6.

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

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

How urgent is this, really

GHSA-3g76-f9xq-8vp6 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.

Where this sits among everything scored

Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.

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

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

    No patched version of io.vertx:vertx-core has shipped for GHSA-3g76-f9xq-8vp6 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-3g76-f9xq-8vp6 can be triaged on real exposure rather than presence alone.

Tailored to GHSA-3g76-f9xq-8vp6. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

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…

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.SP1vertx-coreRHSA-2026:26018
Red Hat build of Quarkus 3.33.2.SP1vertx-coreRHSA-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
O3 Security · Impact-Aware SCA

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GHSA-3g76-f9xq-8vp6: DoS (Medium 5.3) | O3 Security