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CVE-2026-93566 medium CVSS 6.5

### Summary Netty skips strict chunk size line validation when the line has no chunk extension (`...

Summary

Vulnerability reported (CVE-2026-93566). Risk of unauthorized operations or information disclosure. Exploitable via GET /smuggled.

Original description

The description as published by the source.

Summary

Netty skips strict chunk size line validation when the line has no chunk extension (;), so a chunk size line containing an embedded bare CR (e.g. 0\rX) is accepted instead of rejected, enabling HTTP request smuggling.

Details

io.netty.handler.codec.http.HttpObjectDecoder#checkChunkExtensions only runs the strict validator HttpChunkLineValidatingByteProcessor when a ; is present:

        int extensionsStart = line.bytesBefore((byte) ';');
        if (extensionsStart == -1) {
            return;
        }

According to RFC 9112 https://datatracker.ietf.org/doc/html/rfc9112#appendix-A

chunk-size = 1*HEXDIG

PoC

@Test
public void test() {
    String requestStr = "POST / HTTP/1.1\r\n" +
            "Host: localhost\r\n" +
            "Transfer-Encoding: chunked\r\n\r\n" +
            "0\rX\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, Ch

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-2026-93566 has been found.
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: apply the vendor's official patched release.
If unsure, ask your IT team or search "CVE-2026-93566" on the vendor's site.

CVE-2026-93566 — CWE-1035 / CVSS v3 6.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: GET /smuggled / HttpChunkLineValidatingByteProcessor
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-1035) has been reported. Attackers reach the vulnerable code path via GET /smuggled without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions. Attack surface: GET /smuggled / HttpChunkLineValidatingByteProcessor.

🔥 Severity

Severity: Medium (CVSS 6.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ 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 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

  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影響コンポーネントを特定する。

  2. 2
    Hunt 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。

  3. 3
    Post-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。

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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