A flaw was found in Netty. A remote attacker could exploit this by sending a specially crafted HTTP request that includes control characters within the chunk-size line. This bypasses the intended strict validation, allowing the attacker to inject arbitrary HTTP requests. This vulnerability can lead to HTTP request smuggling, potentially resulting in information disclosure or other unauthorized actions.

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Fixes

Solution

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Workaround

See https://github.com/netty/netty/security/advisories/GHSA-rq4j-fc47-9698 for fixed versions and remediation guidance.

History

Sat, 19 Sep 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Moderate


Fri, 18 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
Description ### Summary Netty skips strict chunk size line validation when the line has no chunk extension (`;`), so a chunk size line containing an embedded bare CR (e.g. `0\rX`) is accepted instead of rejected, enabling HTTP request smuggling. ### Details `io.netty.handler.codec.http.HttpObjectDecoder#checkChunkExtensions` only runs the strict validator `HttpChunkLineValidatingByteProcessor` when a `;` is present: ```java int extensionsStart = line.bytesBefore((byte) ';'); if (extensionsStart == -1) { return; } ``` According to RFC 9112 https://datatracker.ietf.org/doc/html/rfc9112#appendix-A `chunk-size = 1*HEXDIG` ### PoC ```java @Test public void test() { String requestStr = "POST / HTTP/1.1\r\n" + "Host: localhost\r\n" + "Transfer-Encoding: chunked\r\n\r\n" + "0\rX\r\n" + "\r\n" + "GET /smuggled HTTP/1.1\r\n" + "Host: localhost\r\n" + "Content-Length: 0\r\n" + "\r\n"; EmbeddedChannel channel = new EmbeddedChannel(new HttpRequestDecoder()); assertTrue(channel.writeInbound(Unpooled.copiedBuffer(requestStr, Ch A flaw was found in Netty. A remote attacker could exploit this by sending a specially crafted HTTP request that includes control characters within the chunk-size line. This bypasses the intended strict validation, allowing the attacker to inject arbitrary HTTP requests. This vulnerability can lead to HTTP request smuggling, potentially resulting in information disclosure or other unauthorized actions.

Fri, 18 Sep 2026 14:30:00 +0000

Type Values Removed Values Added
Description ### Summary Netty skips strict chunk size line validation when the line has no chunk extension (`;`), so a chunk size line containing an embedded bare CR (e.g. `0\rX`) is accepted instead of rejected, enabling HTTP request smuggling. ### Details `io.netty.handler.codec.http.HttpObjectDecoder#checkChunkExtensions` only runs the strict validator `HttpChunkLineValidatingByteProcessor` when a `;` is present: ```java int extensionsStart = line.bytesBefore((byte) ';'); if (extensionsStart == -1) { return; } ``` According to RFC 9112 https://datatracker.ietf.org/doc/html/rfc9112#appendix-A `chunk-size = 1*HEXDIG` ### PoC ```java @Test public void test() { String requestStr = "POST / HTTP/1.1\r\n" + "Host: localhost\r\n" + "Transfer-Encoding: chunked\r\n\r\n" + "0\rX\r\n" + "\r\n" + "GET /smuggled HTTP/1.1\r\n" + "Host: localhost\r\n" + "Content-Length: 0\r\n" + "\r\n"; EmbeddedChannel channel = new EmbeddedChannel(new HttpRequestDecoder()); assertTrue(channel.writeInbound(Unpooled.copiedBuffer(requestStr, Ch
Title Io.netty/netty-codec-http: netty: http request smuggling due to control characters in the chunk-size line
First Time appeared Redhat
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Weaknesses CWE-1035
CPEs cpe:/a:redhat:amq_broker:7
cpe:/a:redhat:amq_clients:2023
cpe:/a:redhat:apicurio_registry:3
cpe:/a:redhat:build_keycloak:
cpe:/a:redhat:camel_quarkus:3
cpe:/a:redhat:camel_spring_boot:4
cpe:/a:redhat:debezium:3
cpe:/a:redhat:jboss_data_grid:8
cpe:/a:redhat:jboss_enterprise_application_platform:7
cpe:/a:redhat:jboss_enterprise_application_platform:8
cpe:/a:redhat:jboss_fuse:7
cpe:/a:redhat:quarkus:3
cpe:/a:redhat:red_hat_single_sign_on:7
Vendors & Products Redhat
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References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-09-18T20:12:32.112Z

Reserved: 2026-09-18T10:00:52.431Z

Link: CVE-2026-93566

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-18T15:17:20.290

Modified: 2026-09-18T21:18:47.507

Link: CVE-2026-93566

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-09-10T00:47:37Z

Links: CVE-2026-93566 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-18T23:45:15Z

Weaknesses