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Critical, CVSS 9.4amended

Prototype pollution in swiper

CVE-2026-27212GHSA-hmx5-qpq5-p643

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (swiper 12.1.2), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm swiper

    Affected
    >= 6.5.1, < 12.1.2
    Fixed in
    12.1.2

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
9.4 · 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 · score source
EPSS
  • CVE-2026-27212: 0.49% estimated exploitation activity in the next 30 days; percentile 41.87 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary A prototype pollution vulnerability exists in the the npm package swiper (=6.5.1, < 12.1.2). 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. This issue is fixed in version 12.1.2 Details The vulnerability resides in line 94 of shared/utils.mjs where indexOf() function is used to check whether user provided input contain forbidden strings. PoC Steps to reproduce 1. Install latest version of swiper using npm install 2. Run the following code snippet: Expected behavior Prototype pollution should be prevented and {} should not gain new properties. This should be printed on the console: Actual behavior Object.prototype is polluted This is printed on the console: Impact This is a prototype pollution vulnerability, which can have severe…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-hmx5-qpq5-p643

  2. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 2 · amended ·

    Amended from osv record GHSA-hmx5-qpq5-p643

  4. Revision 1 · created ·

    Published from ghsa record GHSA-hmx5-qpq5-p643

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-27212

Advisory: Prototype pollution in swiper
IDs: CVE-2026-27212, GHSA-hmx5-qpq5-p643
Record: https://patchnext.com/advisories/cve-2026-27212 (revision 4, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: swiper 12.1.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm swiper: affected >= 6.5.1, < 12.1.2; fixed in 12.1.2

## Suggested inspection (read-only)
- `npm ls swiper --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on swiper.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-hmx5-qpq5-p643 (GitHub-reviewed advisory GHSA-hmx5-qpq5-p643 lists affected ranges: npm swiper >=6.5.1 <12.1.2)
- Verified: https://osv.dev/vulnerability/GHSA-hmx5-qpq5-p643 (OSV record GHSA-hmx5-qpq5-p643 lists affected ranges: npm swiper >=6.5.1 <12.1.2 (fixed))

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