Vulnerability in io.netty:netty-codec-http (CVE-2026-42585)
Summary
Vulnerability in io.netty:netty-codec-http (CVE-2026-42585). Risk of unauthorized operations or information disclosure. Exploitable via GET /smuggled. Mitigation: upgrade to 4.1.133.Final or later.
Original description
The description as published by the source.
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.
@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.copiedB…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-42585 has been found in io.netty:netty-codec-http.
Attackers can target a specific entry point like GET /smuggled over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.5/10.
What to do: upgrade io.netty:netty-codec-http to 4.1.133.Final or later.
If unsure, ask your IT team or search "io.netty:netty-codec-http CVE-2026-42585" on the vendor's site.
CVE-2026-42585 (io.netty:netty-codec-http) — CWE-444 / CVSS v3 6.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: GET /smuggled
Patched: 4.1.133.Final — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-444) exists in io.netty:netty-codec-http. Attackers reach the vulnerable code path via GET /smuggled without authentication.
Check the vendor advisory for the affected versions of io.netty:netty-codec-http. Attack surface: GET /smuggled.
Severity: Medium (CVSS 6.5/10). Risk of unauthorized operations or information disclosure.
Update to 4.1.133.Final.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual GET /smuggled requests with malformed payloads or SQL meta-characters. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで io.netty:netty-codec-http を使っているサービスとバージョンを洗い出す。
-
2Hunt for indicators of compromise detect
grep 'GET /smuggled' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
GET /smuggledへの異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Apply patch patch
Upgrade io.netty:netty-codec-http to 4.1.133.Finalステージング環境で 4.1.133.Final に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。
-
4Post-deployment verification verify
Replay attack against GET /smuggled on staging to confirm patch closes the vectorパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-42585 netty
- Ubuntu UBUNTU-CVE-2026-42585 netty Fixed in: 1:3.2.6.Final-2+deb8u2ubuntu0.1~esm1
References
- advisory nvd.nist.gov
- exploit github.com
- package github.com
- web datatracker.ietf.org
- web github.com