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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-84997?
2 open source packages ship an affected version, including react/http.
| Package | 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.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-84997 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-84997 exists.
Sources
Also known as GHSA-x424-64qh-5j54.