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CVE-2026-42581 medium CVSS 5.8

Vulnerability in io.netty:netty-codec-http (CVE-2026-42581)

Summary

Vulnerability in io.netty:netty-codec-http (CVE-2026-42581). Risk of unauthorized operations or information disclosure. Exploitable via POST /api. Mitigation: upgrade to 4.1.133.Final or later.

Original description

The description as published by the source.

NETTY HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization

Field Value
Library io.netty:netty-codec-http
Component codec-http — HttpObjectDecoder
Severity HIGH
Affects HEAD, commit 4f3533ae confirmed

Summary

HttpObjectDecoder strips a conflicting Content-Length header when a request carries both Transfer-Encoding: chunked and Content-Length, but only for HTTP/1.1 messages. The guard is absent for HTTP/1.0. An attacker that sends an HTTP/1.0 request with both headers causes Netty to decode the body as chunked while leaving Content-Length intact in the forwarded HttpMessage. Any downstream proxy or handler that trusts Content-Length over Transfer-Encoding will disagree on message boundaries, enabling request smuggling.

Root Cause

// HttpObjectDecoder.java:828-833
if (HttpUtil.isTransferEncodingChunked(message)) {
    this.chunked = true;
    if (!contentLengthFields.isEmpty() && message.protocolVersion() == HttpVersion.HTTP_1_1) {
        handleTransferEncodingChunkedWithContentLength(message);  // strips CL — HTTP/1.1 only
    }
    return State.READ_CHUNK_SIZE;
}

// HttpObjectDecoder.java:870-873
protected void handleTransferEncodingChunkedWithContentLength(HttpMessage message) {
    message.headers().remove(HttpHeaderNames.CONTENT_LENGTH);
    contentLength = Long.MIN_VALUE;
}

The conflict-resolution path is gated on `message.protocolVersion() =…

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-2026-42581 has been found in io.netty:netty-codec-http.
Attackers can target a specific entry point like POST /api over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.8/10.
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-2026-42581" on the vendor's site.

CVE-2026-42581 (io.netty:netty-codec-http) — CWE-444 / CVSS v3 5.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: POST /api / HttpObjectDecoder / HttpMessage / EmbeddedChannel
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.

❓ What is the problem

A vulnerability (CWE-444) exists in io.netty:netty-codec-http. Attackers reach the vulnerable code path via POST /api without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of io.netty:netty-codec-http. Attack surface: POST /api / HttpObjectDecoder / HttpMessage / EmbeddedChannel.

🔥 Severity

Severity: Medium (CVSS 5.8/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 4.1.133.Final.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual POST /api 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

  1. 1
    Identify 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。

  2. 2
    Hunt for indicators of compromise detect 
    grep 'POST /api' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで POST /api 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。

  3. 3
    Apply 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。

  4. 4
    Post-deployment verification verify 
    Replay attack against POST /api 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

maven io.netty:netty-codec-http
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.1.133.Final"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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