Vulnerability · CVE-2026-104827
react/http is an event-driven, streaming HTTP client and server implementation for ReactPHP.
Published Oct 15, 2026 · corrected/updated Oct 15, 2026 · evidence confidence high
### Summary and its lower-level HTTP stack impose no limit on the size of a response's header section while it is being received. appends every incoming byte to an internal buffer and only scans that buffer for the (or ) terminator, without ever checking its length. A remote server that withholds the terminator and keeps streaming can grow the client's memory without bound until PHP's is exhausted and the process crashes. This is an unauthenticated, network-reachable denial of service against any application that uses as a client to fetch untrusted or attacker-influenced URLs, including via redirects. ### Details is bound directly to the underlying connection's event, so every byte the peer sends is appended with no size check: The only exit from the buffering state is finding the header terminator or a connection close, so until it arrives the buffer grows monotonically for as long as the peer keeps sending. The codebase already applies this class of limit elsewhere, but not symmetrically. caps incoming **request** headers when acting as a server, and caps the response **body**, but only once the header section has already been parsed into a . Response header reception was the one stage with no limit at all. ### PoC An HTTP server that sends a valid status line and a partial header, then streams indefinitely without ever terminating the header section: A client fetching it, with : Client memory grows steadily until the process dies with inside . ### Impact Remotely triggerable, unauthenticated denial of service against any process using to fetch from an attacker-controlled, compromised or otherwise untrusted endpoint, including one reached through a redirect. No user interaction and no special privileges are required. Because there is no upper bound on the header buffer, a single cheap connection can drive memory arbitrarily high and crash the process, taking down whatever event loop or worker it was running. Confidentiality and integrity are unaffected; availabili
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-104827 is a high public vulnerability record for this product. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether this product is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: react/http (1.0.0 → 1.11.1); react. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: CVSS 7.5, EPSS 0.4%. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-770. Sources contributing to this record: cve_org, epss, github, gitlab. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
Timeline
Detection, updates, and resolution for this record.
Oct 15, 2026 · NIST NVD
Detected
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 d
Oct 15, 2026 · GitHub Advisory Database
Fix available
react/http fixed in 1.11.1
Oct 15, 2026 · GitHub Advisory Database
Fix available
react/http fixed in 1.11.1
Oct 15, 2026 · GitHub Advisory Database
Updated
### Summary and its lower-level HTTP stack impose no limit on the size of a response's header section while it is being received. appends every incoming byte to an internal buffer and only scans that buffer for the (or ) terminator, without ever checking its length. A remote server that withholds the terminator and keeps streaming can grow the client's memory without bound until PHP's is exhausted
Affected
- Packagist react/http1.0.0 → 1.11.1
- composer reactversion unspecified
Sources
- CVE.orgVulnerability recordCVE-2026-104827
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-104827
30-day exploitation probability 0.4%
first.org - GitHub Advisory DatabasePackage advisoryGHSA-g4f2-2pf3-2pwj
GitHub Advisory Database record mirrored by OSV.
github.com - GitLab Advisory DatabasePackage advisoryCVE-2026-104827
React\Http\Browser and its lower-level HTTP stack impose no limit on the size of a response's header section while it is being received. ClientRequestStream::handleData() appends every incoming byte to an internal buffer and only scans that buffer for the \r\n\r\n (or \n\n) terminator, without ever checking its length. A remote server that withholds the terminator and keeps streaming can grow the
advisories.gitlab.com - NIST NVDVulnerability recordCVE-2026-104827
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 ca
nvd.nist.gov - OpenSSF OSV / OSV ScannerPackage advisoryGHSA-g4f2-2pf3-2pwj
react/http: Unbounded HTTP Client Response Header Buffering Leads to Memory Exhaustion DoS
osv.dev