Livewire prior 3.8.3/4.3.4 Dot-Notated Query-String Parser index.js fromQueryString/insertDotNotatedValueIntoData prototype pollution

Summaryinfo

A vulnerability has been found in Livewire and classified as critical. Impacted is the function fromQueryString/insertDotNotatedValueIntoData of the file js/plugins/history/index.js of the component Dot-Notated Query-String Parser. This manipulation causes prototype pollution. This vulnerability is registered as CVE-2026-81887. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability has been found in Livewire and classified as critical. Affected by this vulnerability is the function fromQueryString/insertDotNotatedValueIntoData of the file js/plugins/history/index.js of the component Dot-Notated Query-String Parser. The manipulation 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. The summary by CVE is:

Livewire is a full-stack framework for Laravel. From 3.0.0-beta.1 until 3.8.3 and 4.3.4, the dot-notated query-string parser in js/plugins/history/index.js, including fromQueryString() and insertDotNotatedValueIntoData(), accepts the __proto__, constructor, and prototype path segments and creates inherited objects. Client-side state handlers then access effects.html, effects.js, effects.xjs, and effects.scripts without Object.prototype.hasOwnProperty.call(), allowing inherited attacker-controlled state to be treated as trusted effects. An unauthenticated attacker can craft a URL that, when opened by a user, executes arbitrary JavaScript in the affected application's origin. Exploitation requires user interaction and does not bypass server-side authorization or grant privileges beyond the affected user. This issue is fixed in versions 3.8.3 and 4.3.4.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-81887 since 08/27/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059 according to MITRE ATT&CK.

Upgrading to version 3.8.3 or 4.3.4 eliminates this vulnerability.

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Name

• Livewire

Website

• Product: https://github.com/livewire/livewire/

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