BuilderIO Builder up to 5.2.11/0.25.13 Helper unflatten builder.userAttributes prototype pollution

Summaryinfo

A vulnerability, which was classified as critical, was found in BuilderIO Builder up to 5.2.11/0.25.13. This vulnerability affects the function unflatten of the component Helper. Executing a manipulation of the argument builder.userAttributes can lead to prototype pollution. This vulnerability is handled as CVE-2026-92781. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability has been found in BuilderIO Builder up to 5.2.11/0.25.13 and classified as critical. This vulnerability affects the function unflatten of the component Helper. The manipulation of the argument builder.userAttributes with an unknown input leads to a prototype pollution vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Builder.io Gen2 SDKs through versions 5.2.11 and 0.25.13 contain a prototype pollution vulnerability in the unflatten helper that processes builder.userAttributes query parameters without prototype guards. Attackers can craft preview links with __proto__ or prototype segments to pollute Object.prototype in a visitor's browser when the SDK processes the malicious URL.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-92781 since 09/16/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/16/2026). The MITRE ATT&CK project declares the attack technique as T1059.

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

Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• BuilderIO

Name

• Builder

Version

• 0.25.0
• 0.25.1
• 0.25.2
• 0.25.3
• 0.25.4
• 0.25.5
• 0.25.6
• 0.25.7
• 0.25.8
• 0.25.9
• 0.25.10
• 0.25.11
• 0.25.12
• 0.25.13
• 5.2.0
• 5.2.1
• 5.2.2
• 5.2.3
• 5.2.4
• 5.2.5
• 5.2.6
• 5.2.7
• 5.2.8
• 5.2.9
• 5.2.10
• 5.2.11

Website

• Product: https://github.com/BuilderIO/builder/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Once again VulDB remains the best source for vulnerability data.

Discussion