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CVE-2026-56818 medium CVSS 6.5

Vulnerability in io.netty:netty-codec-redis (CVE-2026-56818)

Summary

Vulnerability in io.netty:netty-codec-redis (CVE-2026-56818). Risk of unauthorized operations or information disclosure. Exploitable via RedisArrayAggregator. Mitigation: upgrade to 4.2.16.Final or later.

Original description

The description as published by the source.

Summary

RedisArrayAggregator clears retained partial aggregate state when the maxNestedArrayDepth limit is exceeded, but it does not clear the same state when the sibling maxElements limit is exceeded. A peer can start a valid RESP array, send a bulk-string child, then send a nested array header longer than the configured maxElements. Netty throws a decoder exception, but the existing partial aggregate remains retained in the handler.

If the application leaves the channel alive after the exception, later messages are still consumed into the pre-error aggregate. The supplied PoV proves both the retained ByteBuf reference and the stale parser state continuation.

Technical Details

RedisArrayAggregator.decode(...) retains non-array messages before adding them to depths.peek().children. In decodeRedisArrayHeader(...), the header.length() > maxElements branch throws immediately:

if (header.length() > maxElements) {
    throw new CodecException("this codec doesn't support longer length than " + maxElements);
}

The immediately following nested-depth branch clears retained aggregate state before throwing:

if (depths.size() >= maxNestedArrayDepth) {
    releaseAndClearDepths();
    throw new CodecException("max nested array depth exceeded: " + maxNestedArrayDepth);
}

The missing cleanup in the first branch leaves retained children and aggregate state reachable after the exception.

PoC

Place the supplied `RedisArrayAggregatorI…

Source: GitHub Security Advisories (Global) 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-2026-56818 has been found in io.netty:netty-codec-redis.
Attackers can target a specific entry point like RedisArrayAggregator 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-redis to 4.2.16.Final or later.
If unsure, ask your IT team or search "io.netty:netty-codec-redis CVE-2026-56818" on the vendor's site.

CVE-2026-56818 (io.netty:netty-codec-redis) — CWE-401 / CVSS v3 6.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: RedisArrayAggregator / maxNestedArrayDepth / maxElements / ByteBuf
Patched: 4.2.16.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-401) exists in io.netty:netty-codec-redis. Attackers reach the vulnerable code path via RedisArrayAggregator without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of io.netty:netty-codec-redis. Attack surface: RedisArrayAggregator / maxNestedArrayDepth / maxElements / ByteBuf.

🔥 Severity

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

🔧 How to fix

Update to 4.2.16.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 request patterns matching this CVE's known IOCs. 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-redis を使っているサービスとバージョンを洗い出す。

  2. 2
    Apply patch patch 
    Upgrade io.netty:netty-codec-redis to 4.2.16.Final

    ステージング環境で 4.2.16.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を含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    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。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

maven io.netty:netty-codec-redis
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.2.16.Final"}]}]

References

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