CVE-2026-15076

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

1. 2026-07-14 09:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-24 22:10 UTC Last updatedMost recent change to the record

Details

Published

2026-07-14 09:16 UTC

Last modified

2026-10-24 22:10 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-346

Record status

Analyzed

Affected

• Eclipse vert.x ≤ 4.5.29
• Eclipse vert.x ≤ 5.1.4

Attack profile CVSS 4.0 · 8.2

Attack vector

Network

Complexity

Low

Attack requirements

Present

Privileges needed

None

User interaction

None

Confidentiality

High

Integrity

None

Availability

None