multiparty vulnerable to Denial of Service via Uncaught Exception in filename* parameter parsing

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-8162: 0.33% estimated exploitation activity in the next 30 days; percentile 25.65 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact multiparty@4.2.3 and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a Content-Disposition: filename=utf-8'' header containing a malformed percent-encoding (e.g., %FF, %GG), the parser invokes decodeURI on the value without try/catch. The resulting URIError propagates as an uncaught exception and crashes the process. Any service accepting multipart uploads via multiparty is affected. Patches Users should upgrade to multiparty@4.3.0 or higher. Workarounds None.

Published by the source

18 May 2026, 17:35 UTC

Last modified by the source

23 May 2026, 21:35 UTC

Source last checked

26 Oct 2026, 12:52 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-xh3c-6gcq-g4rv

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-xh3c-6gcq-g4rv

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# Patch Next advisory brief: CVE-2026-8162

Advisory: multiparty vulnerable to Denial of Service via Uncaught Exception in filename* parameter parsing
IDs: CVE-2026-8162, GHSA-xh3c-6gcq-g4rv
Record: https://patchnext.com/advisories/cve-2026-8162 (revision 2, source checked 26 Oct 2026, 12:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: multiparty 4.3.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm multiparty: affected <= 4.2.3; fixed in 4.3.0

## Suggested inspection (read-only)
- `npm ls multiparty --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 multiparty.
- 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://osv.dev/vulnerability/GHSA-xh3c-6gcq-g4rv (OSV record GHSA-xh3c-6gcq-g4rv lists affected ranges: npm multiparty >=0 <4.3.0 (fixed))
- Verified: https://github.com/advisories/GHSA-xh3c-6gcq-g4rv (GitHub-reviewed advisory GHSA-xh3c-6gcq-g4rv lists affected ranges: npm multiparty >=0 <=4.2.3)

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