The vulnerability CVE-2026-27212 in the nolimits4web swiper package is a Prototype Pollution flaw classified under CWE-1321. Swiper is a widely used mobile touch slider library with hardware-accelerated transitions. The vulnerability exists in the input validation logic within shared/utils.mjs, specifically around line 94, where the indexOf() function is used to detect forbidden strings in user input. Despite a prior fix attempting to block prototype pollution by filtering forbidden keys, attackers can still exploit the vulnerability by crafting inputs that manipulate Array.prototype, thereby polluting Object.prototype. This pollution allows attackers to alter the behavior of JavaScript objects globally within the application context. The impact of such pollution can be severe, enabling authentication bypass, denial of service, and remote code execution (RCE). The vulnerability affects swiper versions from 6.5.1 up to but not including 12.1.2. It is exploitable on both Windows and Linux environments and works on Node and Bun JavaScript runtimes. No authentication or user interaction is required for exploitation, increasing the risk. The vulnerability has a CVSS 4.0 score of 9.4 (critical), reflecting its high impact and ease of exploitation. The issue is fixed in swiper version 12.1.2, and users are strongly advised to upgrade. No known exploits in the wild have been reported yet, but the potential impact is significant.

The impact of this vulnerability is substantial for organizations worldwide using the swiper package in their web or mobile applications. Prototype pollution can lead to widespread application instability and security breaches by allowing attackers to modify core JavaScript object prototypes. This can result in authentication bypass, enabling attackers to impersonate users or escalate privileges. Denial of service attacks can disrupt application availability by causing unexpected behavior or crashes. Remote code execution could allow attackers to execute arbitrary code on the server or client, potentially compromising entire systems and networks. Since swiper is a popular library integrated into many applications, the attack surface is broad. The vulnerability affects both Windows and Linux platforms and multiple JavaScript runtimes, increasing the scope of affected environments. Organizations that fail to patch may face data breaches, service outages, and reputational damage. The lack of required authentication and user interaction makes automated exploitation feasible, increasing the urgency for remediation.

To mitigate this vulnerability, organizations should immediately upgrade the swiper package to version 12.1.2 or later, where the issue is fixed. For environments where immediate upgrade is not feasible, implement strict input validation and sanitization on all user-supplied data before it reaches the swiper library, focusing on preventing prototype pollution vectors such as keys like '__proto__' or 'constructor'. Employ runtime security controls such as JavaScript sandboxing or object freezing to limit prototype modifications. Monitor application logs for unusual behavior indicative of prototype pollution exploitation attempts. Conduct thorough code reviews and dependency audits to identify and remediate other potential prototype pollution risks. Additionally, apply web application firewalls (WAFs) with custom rules to detect and block suspicious payloads targeting prototype pollution. Educate development teams about secure coding practices related to prototype pollution and maintain an up-to-date inventory of third-party dependencies to ensure timely patching.