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CVE-2026-73508 medium CVSS 5.3

Vulnerability in io.netty:netty-codec-dns (CVE-2026-73508)

Summary

Vulnerability in io.netty:netty-codec-dns (CVE-2026-73508). Risk of unauthorized operations or information disclosure. Exploitable via IDN.toASCII. Mitigation: upgrade to 4.1.136.Final or later.

Original description

The description as published by the source.

Summary

A memory leak can be caused in Netty's DNS codec by sending malicious DNS packets containing invalid domain names. Because the leak occurs incrementally per packet, sustained malicious requests will cause a gradual Denial of Service.

Details

Inside io.netty.handler.codec.dns.AbstractDnsRecord, the parsed domain name string is passed to IDN.toASCII(name). If the domain name contains characters that violate IDNA rules, IDN.toASCII throws an IllegalArgumentException.

Because this exception occurs inside the constructor before the DnsRecord instance can assign the buffer to its content field for later release, the ByteBuf whose reference count was incremented (or newly allocated) is never released, resulting in a direct memory leak.

There are several places where variants of this leak happen:

  • io.netty.handler.codec.dns.DefaultDnsRecordDecoder#decodeRecord(java.lang.String, io.netty.handler.codec.dns.DnsRecordType, int, long, io.netty.buffer.ByteBuf, int, int) invokes in.retainedDuplicate() or creates a new buffer out when constructing DefaultDnsRawRecord
  • io.netty.handler.codec.dns.DnsCodecUtil#decompressDomainName allocates a new ByteBuf and passes it to encodeDomainName(). If the decompressed domain name contains a null byte (\0), encodeDomainName() throws an IllegalArgumentException, leaking the newly allocated buffer.

Impact

Resource Exhaustion. Any application utilizing Netty's DnsRecordDecoder (such as DnsNameResolver…

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-2026-73508 has been found in io.netty:netty-codec-dns.
Attackers can target a specific entry point like IDN.toASCII over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade io.netty:netty-codec-dns to 4.1.136.Final or later.
If unsure, ask your IT team or search "io.netty:netty-codec-dns CVE-2026-73508" on the vendor's site.

CVE-2026-73508 (io.netty:netty-codec-dns) — CWE-772 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: IDN.toASCII / IllegalArgumentException / DnsRecord / out
Patched: 4.1.136.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-772) exists in io.netty:netty-codec-dns. Attackers reach the vulnerable code path via IDN.toASCII without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of io.netty:netty-codec-dns. Attack surface: IDN.toASCII / IllegalArgumentException / DnsRecord / out.

🔥 Severity

Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 4.1.136.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-dns 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-dns to 4.1.136.Final

    ステージング環境で 4.1.136.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-dns
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.1.136.Final"}]}]

References

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