# CVE-2026-15076: Other in Eclipse Vert.x

> Attackers can inject cookies into the Vert.x WebClientSession, causing sensitive data to be sent to attacker-controlled accounts on third-party services.

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Jul 2026
- **Updated:** 14 Jul 2026
- **Also known as:** GHSA-vjx2-fp9g-q2mc

## What is CVE-2026-15076?

CVE-2026-15076 is a high-severity vulnerability in Eclipse Vert.x, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In versions up to and including 4.5.29 (4.x branch) and 5.1.4 (5.x branch), the WebClientSession component of Eclipse Vert.x Web Client does not validate that the Domain attribute of a Set-Cookie response header matches the originating server's domain, in violation of RFC 6265 section 5.3.
An attacker who controls any server that the victim application contacts can inject a cookie scoped to an arbitrary third-party domain; because the session store performs no cross-domain ownership check, it stores and later transmits that cookie to the targeted domain.

When the victim application subsequently sends a request to the targeted domain using the same WebClientSession, it presents the attacker-injected cookie, causing the receiving service to process the request under the attacker's account. Sensitive data included in the victim application's requests, such as payment amounts, card details, or other API payloads, may then be accessible to the attacker through their own account on that service.

Weakness: CWE-346 (Origin Validation Error)

## Which versions are affected by CVE-2026-15076?

It affects 1 product.


Products: Eclipse Vert.x.

## How do I fix CVE-2026-15076?

No fix has been published for CVE-2026-15076 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-15076 being exploited?

There is no known exploitation of CVE-2026-15076 in the wild and no public exploit code.

## Other vulnerabilities in Eclipse Vert.x

- [CVE-2019-17640](https://insights.sbomify.com/CVE-2019-17640/): Path Traversal in Eclipse Vert (critical 9.8)
- [CVE-2018-12542](https://insights.sbomify.com/CVE-2018-12542/): Eclipse Vert.x does not properly neutralize '' (forward slashes) sequences that can resolve to an external location (critical 9.8)
- [CVE-2018-12544](https://insights.sbomify.com/CVE-2018-12544/): Moderate severity vulnerability that affects io.vertx:vertx-core (critical 9.8)
- [CVE-2026-102469](https://insights.sbomify.com/CVE-2026-102469/): Deserialization in Eclipse Vert.x (critical 9.2)
- [CVE-2018-12540](https://insights.sbomify.com/CVE-2018-12540/): High severity vulnerability that affects io.vertx:vertx-web (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-15076 and fix it if it is affected.

What it is: CVE-2026-15076 is a high-severity vulnerability in Eclipse Vert.x, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-15076 in the wild and no public exploit code.

Affected product: Eclipse Vert.x. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-15076/ (Markdown: https://insights.sbomify.com/CVE-2026-15076/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-15076
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-15076
- OSV: https://osv.dev/vulnerability/CVE-2026-15076

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-15076/
Summaries are generated and may contain mistakes; the official description above is the record.