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title: CVE-2026-111181: Denial of service in body-parser
description: A denial-of-service flaw in Express's body-parser middleware lets a malicious client crash a server with a single request. The decompression stream outlives...
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# CVE-2026-111181: Denial of service in body-parser

**[Express.js](https://daily.dev/sources/expressjs-blog)** · 3 min read · 0 upvotes · 0 comments

## Summary

A denial-of-service flaw in Express's body-parser middleware lets a malicious client crash a server with a single request. The decompression stream outlives request parsing, so body-parser hands off control without attaching an error listener to the stream. A payload with a valid gzip member followed by a zero byte and trailing bytes triggers an uncaught exception that crashes the process. Affected versions are body-parser 2.0.0 through 2.3.0 and 1.20.8 and earlier. Fixes landed in 2.4.0 and 1.20.9; disabling inflate rejects compressed bodies as a workaround.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://expressjs.com/en/blog/2026-10-28-cve-2026-111181>

## Questions this post answers

### What is CVE-2026-111181 and how does it crash a Node.js server?

It is a denial-of-service vulnerability in Express's body-parser middleware where a decompression stream outlives request parsing. Body-parser hands off control to the next middleware without attaching an error listener to the decoder. A request with a valid gzip member followed by a zero byte and trailing bytes later triggers an uncaught exception, crashing the process with a single request.

_Track critical Express and Node.js advisories like this on daily.dev before they hit production._

### Which versions of body-parser are vulnerable to the gzip decompression DoS and what should I upgrade to?

Vulnerable versions are body-parser 2.0.0 through 2.3.0 and 1.20.8 and earlier. The fix shipped in body-parser 2.4.0 and 1.20.9. If upgrading immediately isn't possible, setting the inflate option to false rejects compressed request bodies before a decompression stream is created, though it also blocks legitimate compressed requests.

_Developers patching dependency CVEs rely on daily.dev to catch fixed-version details fast._

### Why does a crafted gzip payload with trailing bytes crash an Express app using body-parser?

Once the decoder finishes decompressing a valid gzip member, raw-body returns the decoded payload and detaches its event listeners, including the error listener, then body-parser calls next() while the request stream stays piped into the now-finished decoder. Trailing bytes after the gzip member then cause the decoder to emit an error with no listener left to catch it except pipe()'s re-emitter, so Node treats it as an uncaught exception.

_Engineers debugging stream and middleware edge cases follow writeups like this via daily.dev._

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---

Tags: [#security](https://daily.dev/tags/security), [#cyber](https://daily.dev/tags/cyber), [#nodejs](https://daily.dev/tags/nodejs), [#express](https://daily.dev/tags/express)

[View this post on daily.dev](https://daily.dev/posts/cve-2026-111181-denial-of-service-in-body-parser-narogjw7n)

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