brikcss merge up to 1.3.0 __proto__/constructor.prototype/prototype prototype pollution

Summaryinfo

A vulnerability marked as problematic has been reported in brikcss merge up to 1.3.0. This vulnerability affects unknown code. The manipulation of the argument __proto__/constructor.prototype/prototype leads to prototype pollution. This vulnerability is traded as CVE-2026-6594. It is possible to initiate the attack remotely. There is no exploit available. The vendor was contacted early about this disclosure but did not respond in any way.

Detailsinfo

A vulnerability, which was classified as critical, has been found in brikcss merge up to 1.3.0. This issue affects an unknown code. The manipulation of the argument __proto__/constructor.prototype/prototype with an unknown input leads to a prototype pollution vulnerability. Using CWE to declare the problem leads to CWE-1321. The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. Impacted is confidentiality, integrity, and availability.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-6594. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. 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 04/20/2026). MITRE ATT&CK project uses the attack technique T1059 for this issue.

The vendor was contacted early about this disclosure but did not respond in any way.

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

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-23742). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Vendor

• brikcss

Name

• merge

Version

• 1.0
• 1.1
• 1.2
• 1.3.0

CPE 2.3info

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CPE 2.2info

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Submitinfo

Accepted

• Submit #791805: brikcss @brikcss/merge 1.3.0 Prototype Pollution (by sudosme)

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

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