CVE-2026-104827 react/http: Unbounded HTTP Client Response Header Buffering Leads to Memory Exhaustion DoS
A remote server can cause memory exhaustion and crash the application by streaming unbounded HTTP response headers to the ReactPHP HTTP client.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-104827?
CVE-2026-104827 is a high-severity denial of service vulnerability in reactphp http, published on 15 Oct 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 1.0.0 until 1.11.1, React\Http\Browser uses ClientRequestStream::handleData() to append response-header bytes to an internal buffer without enforcing a size limit. A remote server can send a valid status line and partial header, withhold the \r\n\r\n or \n\n header terminator, and continue streaming data so the buffer grows for the life of the connection. Applications that fetch attacker-controlled or attacker-influenced URLs, including URLs reached through redirects, can exhaust PHP memory_limit and crash the event-loop or worker process. Confidentiality and integrity are unaffected. This issue is fixed in version 1.11.1.
Weakness: CWE-770
Which versions are affected by CVE-2026-104827?
2 open source packages ship an affected version, including react/http.
| Package | Affected | Fixed in |
|---|---|---|
react/http Packagist | From 1.0.0 | 1.11.1 |
react/http Packagist | From 1.0.0 | 1.11.1 |
How do I fix CVE-2026-104827?
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-2026-104827 being exploited?
There is no known exploitation of CVE-2026-104827 in the wild and no public exploit code.
Sources
Also known as GHSA-g4f2-2pf3-2pwj, UBUNTU-CVE-2026-104827.