GHSA-q7qp-rjg7-q26m: High severity npm/multer vulnerability

Q: Which deployments are exposed to this denial-of-service issue?

Any application using multer with an asynchronous fileFilter is affected, regardless of the storage engine. Upload handlers using a synchronous fileFilter are not affected.

Q: Does an attacker need credentials or user interaction to trigger the crash?

No. A single unauthenticated request can trigger the issue, with no user interaction required.

Q: What conditions are needed to trigger the process exit?

A request must be aborted while one file is rejected and another file's asynchronous fileFilter callback is still pending. When that callback later resumes parsing, busboy emits an unhandled error and the Node.js process exits.

Q: What can be done if upgrading is not immediately possible?

Replace the asynchronous fileFilter with a synchronous fileFilter. This avoids the affected code path.

Q: What version fixes the issue?

Upgrade multer to version 2.5.0 or later.

Published Oct 23, 2026

Updated

Impact

When multer is configured with an asynchronous fileFilter, a single request can crash the Node.js process. If a request is aborted (for example when one file is rejected) while another file's async fileFilter is still pending, the pending callback later resumes a parsing stream that multer has already torn down. busboy then emits an error on a stream that no longer has an error listener, which Node raises as an unhandled 'error' event, and the process exits. A single unauthenticated request is enough, so any application using multer with an asynchronous fileFilter is affected, regardless of storage engine. Uploads using a synchronous fileFilter are not affected.

Patches

Users should upgrade to multer 2.5.0 or later.

Workarounds

Use a synchronous fileFilter.

Affected Software

1 affected componentFixes available

npm/multer>=2.0.0<2.5.0

2.5.0

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade npm/multer to a version that resolves this vulnerability.
Fixed in 2.5.0
Upgrade
Upgrade multer to a version that resolves this vulnerability.
Fixed in 2.5.0
Configuration
Use a synchronous fileFilter instead of an asynchronous fileFilter.
multer fileFilter = synchronous

Event History

Oct 23, 2026

Advisory Published

via GitHub·10:08 PM

Data Sourced

via GitHub·10:08 PM

DescriptionSeverityWeaknessAffected Software

Frequently Asked Questions

Which deployments are exposed to this denial-of-service issue?

Any application using multer with an asynchronous fileFilter is affected, regardless of the storage engine. Upload handlers using a synchronous fileFilter are not affected.

Does an attacker need credentials or user interaction to trigger the crash?

No. A single unauthenticated request can trigger the issue, with no user interaction required.

What conditions are needed to trigger the process exit?

A request must be aborted while one file is rejected and another file's asynchronous fileFilter callback is still pending. When that callback later resumes parsing, busboy emits an unhandled error and the Node.js process exits.

What can be done if upgrading is not immediately possible?

Replace the asynchronous fileFilter with a synchronous fileFilter. This avoids the affected code path.

What version fixes the issue?

Upgrade multer to version 2.5.0 or later.

GHSA-q7qp-rjg7-q26m: High severity npm/multer vulnerability

Affected Software

Remediation

Event History

Frequently Asked Questions

Which deployments are exposed to this denial-of-service issue?

Does an attacker need credentials or user interaction to trigger the crash?

What conditions are needed to trigger the process exit?

What can be done if upgrading is not immediately possible?

What version fixes the issue?

Company

Resources

Contact

Frequently Asked Questions

Which deployments are exposed to this denial-of-service issue?

Does an attacker need credentials or user interaction to trigger the crash?

What conditions are needed to trigger the process exit?

What can be done if upgrading is not immediately possible?

What version fixes the issue?