Vulnerability · Published Sep 16, 2026 · Assigned by VulnCheck

CVE-2026-92781Builder.io Gen2 SDKs through 5.2.11 Prototype Pollution via builder.userAttributes

Medium 6.3

In plain English

A medium-severity prototype pollution in @builder.io/sdk-angular from BuilderIO. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 30% of all known vulnerabilities).

Severity (CVSS 3.1)6.3Medium

Exploit odds (30 days)0.4%top 70.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

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.

Affected products (as reported)

Vendor	Product	Versions
BuilderIO	@builder.io/sdk-react	0 – through 5.2.11
BuilderIO	@builder.io/sdk-vue	0 – through 5.2.11
BuilderIO	@builder.io/sdk-svelte	0 – through 5.2.11
BuilderIO	@builder.io/sdk-solid	0 – through 5.2.11
BuilderIO	@builder.io/sdk-qwik	0 – through 0.25.13
BuilderIO	@builder.io/sdk-angular	0 – through 0.25.13
BuilderIO	@builder.io/sdk-react-nextjs	0 – through 0.25.13

Weakness: CWE-1321 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L

References

GitHub Issue #4824 issue-tracking
https://github.com/BuilderIO/builder product
builder.userAttributes parameters are expanded through unflatten technical-description
unflatten walks the dotted key path with no prototype guard technical-description
VulnCheck Advisory: Builder.io Gen2 SDKs through 5.2.11 Prototype Pollution via builder.userAttributes third-party-advisory