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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-84997: 0.66% estimated exploitation activity in the next 30 days; percentile 51.43 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A malformed HTTP message using Transfer-Encoding: chunked can drive React\Http\Io\ChunkedDecoder into an infinite loop, pegging a CPU core and freezing the event loop. Because ReactPHP is single-threaded, one such message stalls the entire process for every client until it is killed. Both directions are affected. ChunkedDecoder decodes chunked request bodies for React\Http\HttpServer and chunked response bodies for React\Http\Browser, so a server can be attacked by a malicious client and a client can be attacked by a malicious or compromised server. Details ChunkedDecoder::handleData() loops while ($this-buffer !== '') and relies on the buffer shrinking each iteration. Two states leave the buffer unchanged while the loop condition stays true. Terminal-chunk trailer. After the terminating 0 chunk, any remaining buffer is treated as trailer data to skip: When the trailer holds no CRLF yet, strpos() returns false, PHP coerces that to 0 in substr(), and the buffer is never…

Published by the source

17 Sep 2026, 20:32 UTC

Last modified by the source

17 Sep 2026, 20:45 UTC

Source last checked

26 Oct 2026, 14:53 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-x424-64qh-5j54

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-x424-64qh-5j54

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# Patch Next advisory brief: CVE-2026-84997

Advisory: react/http: A malformed HTTP chunked body can lead to a denial-of-service and peg the CPU
IDs: CVE-2026-84997, GHSA-x424-64qh-5j54
Record: https://patchnext.com/advisories/cve-2026-84997 (revision 2, source checked 26 Oct 2026, 14:53 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: react/http 1.11.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist react/http: affected >= 0.6.0, <= 1.11.0; fixed in 1.11.1

## Suggested inspection (read-only)
- Packagist react/http: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on react/http.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-x424-64qh-5j54 (OSV record GHSA-x424-64qh-5j54 lists affected ranges: Packagist react/http >=0.6.0 <1.11.1 (fixed))
- Verified: https://github.com/advisories/GHSA-x424-64qh-5j54 (GitHub-reviewed advisory GHSA-x424-64qh-5j54 lists affected ranges: Packagist react/http >=0.6.0 <=1.11.0)

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