CVE-2026-92781 BuilderIO CVE debrief

Who should care

Defenders responsible for maintaining and securing applications built with Builder.io Gen2 SDKs should assess exposure and prioritize verification and updates to affected SDK versions.

Why it matters

CVE-2026-92781 is a medium-severity vulnerability affecting Builder.io Gen2 SDKs. Defenders should assess exposure, prioritize verification and updates to affected SDK versions, and implement compensating controls to mitigate potential impacts. The vulnerability allows attackers to pollute Object.prototype in visitor browsers, potentially affecting application behavior and security.

• Potential pollution of Object.prototype in visitor browsers.
• Possible impact on application behavior and security.
• Need for verification of affected versions and exposure.
• Priority for updating affected SDK versions.

Technical summary

The vulnerability is caused by a lack of prototype guards in the unflatten helper that processes builder.userAttributes query parameters. This allows attackers to 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 product deployments should be verified, and owners should assess exposure and prioritize verification and updates to affected SDK versions. Compensating controls should be implemented to mitigate potential impacts.

Defensive priority

Defenders should prioritize verifying and updating affected SDK versions, assessing exposure in their environments, and implementing compensating controls to mitigate potential impacts.

Recommended defensive actions

• Verify and update affected SDK versions to a fixed version, if available.
• Assess exposure in environments using the affected SDK versions.
• Implement compensating controls to mitigate potential impacts.
• Monitor for suspicious activity related to the vulnerability.
• Review relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its description, CVSS score, and affected versions. However, the corpus does not establish versions beyond 5.2.11 and 0.25.13, exploitation, impact, or remediation, which require verification from the supplied official sources.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.