Eclipse Vert.x up to 4.5.29/5.1.4 WebClientSession Domain cross-domain policy

Summaryinfo

A vulnerability has been found in Eclipse Vert.x up to 4.5.29/5.1.4 and classified as problematic. Affected by this issue is some unknown functionality of the component WebClientSession. The manipulation of the argument Domain leads to cross-domain policy. This vulnerability is traded as CVE-2026-15076. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in Eclipse Vert.x up to 4.5.29/5.1.4. It has been rated as problematic. This issue affects an unknown part of the component WebClientSession. The manipulation of the argument Domain with an unknown input leads to a cross-domain policy vulnerability. Using CWE to declare the problem leads to CWE-942. The product uses a cross-domain policy file that includes domains that should not be trusted. Impacted is confidentiality. The summary by CVE 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.

The advisory is shared at gitlab.eclipse.org. The identification of this vulnerability is CVE-2026-15076 since 07/08/2026. The exploitation is known to be difficult. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/14/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Vendor

• Eclipse

Name

• Vert.x

Version

• 4.5.0
• 4.5.1
• 4.5.2
• 4.5.3
• 4.5.4
• 4.5.5
• 4.5.6
• 4.5.7
• 4.5.8
• 4.5.9
• 4.5.10
• 4.5.11
• 4.5.12
• 4.5.13
• 4.5.14
• 4.5.15
• 4.5.16
• 4.5.17
• 4.5.18
• 4.5.19
• 4.5.20
• 4.5.21
• 4.5.22
• 4.5.23
• 4.5.24
• 4.5.25
• 4.5.26
• 4.5.27
• 4.5.28
• 4.5.29
• 5.1.0
• 5.1.1
• 5.1.2
• 5.1.3
• 5.1.4

License

• open-source

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CPE 2.2info

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