EUVD-2026-82935
GHSA-9mrj-55p4-qwf4
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Network unauthenticated parser flaw, but reliable smuggling requires a differing upstream/downstream HTTP intermediary (topology dependency), so AC:H; limited confidentiality and integrity impact via request desync, no availability effect.
Primary rating from Vendor (redhat).
CVSS VectorVendor: redhat
Lifecycle Timeline
3DescriptionCVE.org
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:
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
@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, ChAnalysisAI
HTTP request smuggling in Netty's HTTP/1.1 decoder (HttpObjectDecoder and the HttpRequestDecoder built on it) lets remote, unauthenticated attackers send a chunk-size line containing an embedded bare carriage return - for example 0\rX - because strict chunk-line validation is skipped whenever the size line carries no ; chunk extension, causing a request-boundary desync when Netty shares a connection with a second HTTP intermediary that frames the message differently. The flaw reaches every application and Red Hat product that embeds Netty, including AMQ Broker 7, AMQ Clients, Quarkus, Camel 4 for Quarkus 3, Camel for Spring Boot 4, Keycloak / Red Hat Single Sign-On, JBoss EAP 7 and 8, Fuse 7, Data Grid 8, Apicurio Registry 3 and Debezium 3, while independent assessment keeps it at CVSS 6.5 with AC:H because a standalone Netty service with no disagreeing proxy in the chain yields little practical smuggling impact. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that Netty's HTTP decoder (HttpObjectDecoder / HttpRequestDecoder) parse attacker-supplied requests, and - critically - that Netty be deployed behind or in front of another HTTP intermediary (reverse proxy, load balancer, or CDN) that disagrees on chunk-line framing, so the bare-CR chunk-size line ('0\rX', no ';' chunk extension) causes a request-boundary desync. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a genuine but moderate-priority integrity flaw. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | The correct fix is upstream, in Netty's HttpObjectDecoder: remove the early `return` when `bytesBefore((byte) ';')` yields -1 so that HttpChunkLineValidatingByteProcessor always validates the chunk-size line, not only lines containing a chunk extension - upgrading to a Netty release that carries this correction is the primary remediation. … Detailed patch versions, workarounds, and compensating controls in full report. |
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