# CVE-2026-84997: react/http: A malformed HTTP chunked body can lead to a denial-of-service and peg the CPU

> A malformed HTTP chunked body causes an infinite loop in the ReactPHP HTTP library, allowing attackers to freeze servers or clients via CPU exhaustion.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Sep 2026
- **Updated:** 16 Sep 2026
- **Also known as:** GHSA-x424-64qh-5j54

## What is CVE-2026-84997?

CVE-2026-84997 is a high-severity denial of service vulnerability in reactphp http, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

react/http is an event-driven, streaming HTTP client and server implementation for ReactPHP. From 0.6.0 until 1.11.1, React\Http\Io\ChunkedDecoder could enter an infinite loop while processing a malformed Transfer-Encoding: chunked body because handleData required its buffer to shrink on every iteration. An incomplete terminal-chunk trailer without CRLF left the buffer unchanged after strpos returned false, and exactly two non-CRLF bytes after a completed non-terminal chunk bypassed both the error and wait guards. The affected decoder processes request bodies for React\Http\HttpServer and response bodies for React\Http\Browser, allowing a malicious client to freeze a server or a malicious or compromised server to freeze a client. A reverse proxy that normalizes inbound requests may protect the server direction but does not protect outbound Browser requests. This issue is fixed in version 1.11.1.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2026-84997?

2 open source packages ship an affected version, including react/http.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `react/http` | Packagist | From 0.6.0 | 1.11.1 |
| `react/http` | Packagist | From 0.6.0 | 1.11.1 |

## How do I fix CVE-2026-84997?

Upgrade react/http to 1.11.1 or later.

## Is CVE-2026-84997 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-84997 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-84997 and fix it if it is affected.

What it is: CVE-2026-84997 is a high-severity denial of service vulnerability in reactphp http, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-84997 exists.

Affected packages and fixed versions:
- react/http (Packagist): affected from 0.6.0; fixed in 1.11.1
- react/http (Packagist): affected from 0.6.0; fixed in 1.11.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-84997/ (Markdown: https://insights.sbomify.com/CVE-2026-84997/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-84997
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-84997
- OSV: https://osv.dev/vulnerability/CVE-2026-84997

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-84997/
Summaries are generated and may contain mistakes; the official description above is the record.