CVE-2026-73508: Netty Memory Leak Vulnerability

MODERATE
Advisory Identifier: GHSA-mfg7-5gfp-c4w3
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CVSS 5.3
CWE-772
Published
Advisory Summary

CVE-2026-73508 is a MODERATE (CVSS 5.3) memory leak vulnerability (CWE-772: Missing Release of Resource after Effective Lifetime) affecting Netty libraries in the Maven ecosystem. The issue involves memory leak in dns record decoder via malformed domain names. Remediation is available by upgrading affected packages to version 4.2.16.Final, 4.1.136.Final.

CVE-2026-73508 at a Glance

CVE Identifier CVE-2026-73508
GHSA Identifier GHSA-mfg7-5gfp-c4w3
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-772: Missing Release of Resource after Effective Lifetime
Affected Product Netty
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 5.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability Low (A:L)

How to Fix CVE-2026-73508

To remediate this vulnerability, upgrade all affected Netty dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

io.netty:netty-codec-dns fixed: 4.2.16.Final 
<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-codec-dns</artifactId>
    <version>4.2.16.Final</version>
</dependency>
io.netty:netty-codec-dns fixed: 4.1.136.Final 
<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-codec-dns</artifactId>
    <version>4.1.136.Final</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=io.netty

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-73508, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=io.netty

Analyze the terminal output to locate any version of Netty in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.2.16.Final), your application is affected.

Note: The mvn dependency:tree -Dincludes=io.netty command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-772: Missing Release of Resource after Effective Lifetime, where the product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed. In Netty, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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 or custom DNS servers) is vulnerable.

CVE-2026-73508 Affected Netty Versions

2 component(s)
Fixed Versions:
4.2.16.Final4.1.136.Final
Product / Package Ecosystem Affected Versions Fixed Version
io.netty:netty-codec-dns
maven/io.netty/netty-codec-dns
Maven
≥ 4.2.0.Final
< 4.2.16.Final
4.2.16.Final
io.netty:netty-codec-dns
maven/io.netty/netty-codec-dns
Maven
< 4.1.136.Final
4.1.136.Final

References

GitHub Advisory / Wiki ADVISORY
https://github.com/netty/netty/security/advisories/GHSA-mfg7-5gfp-c4w3
Netty Source Repository REPOSITORY
https://github.com/netty/netty/pull/17063
Netty Source Repository REPOSITORY
https://github.com/netty/netty/pull/17065
Security Fix Commit FIX COMMIT
https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b
Security Fix Commit FIX COMMIT
https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6
Netty Source Repository REPOSITORY
https://github.com/netty/netty
Netty Release RELEASE
https://github.com/netty/netty/releases/tag/netty-4.1.136.Final
Netty Release RELEASE
https://github.com/netty/netty/releases/tag/netty-4.2.16.Final

Frequently Asked Questions

What is CVE-2026-73508?
CVE-2026-73508 is a security vulnerability in Netty involving Memory Leak in DNS Record Decoder via Malformed Domain Names under CWE-772: Missing Release of Resource after Effective Lifetime.
Which Netty versions are affected?
Affected versions include releases prior to 4.2.16.Final, 4.1.136.Final across affected packages: io.netty:netty-codec-dns.
What version fixes CVE-2026-73508?
Upgrading to 4.2.16.Final, 4.1.136.Final (or the latest patched release for your respective branch) resolves the vulnerability.
Is netty-codec-dns affected?
Yes, io.netty:netty-codec-dns is affected in releases prior to 4.2.16.Final, 4.1.136.Final. Upgrade your dependency to 4.2.16.Final, 4.1.136.Final or later.
What is the CVSS score of CVE-2026-73508?
CVE-2026-73508 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
What CWE is associated with CVE-2026-73508?
CVE-2026-73508 is classified under CWE-772: Missing Release of Resource after Effective Lifetime (The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.).
How can I check Maven dependencies for CVE-2026-73508?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=io.netty'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mfg7-5gfp-c4w3",
  "modified" : "2026-08-13T14:27:40Z",
  "published" : "2026-07-24T16:52:50Z",
  "aliases" : [ "CVE-2026-73508" ],
  "summary" : "Netty: Memory Leak in DNS Record Decoder via Malformed Domain Names",
  "details" : "### Summary\nA 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.\n\n### Details\nInside `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`.\n\nBecause 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.\n\nThere are several places where variants of this leak happen:\n- `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`\n- `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.\n\n### Impact\nResource Exhaustion. Any application utilizing Netty's DnsRecordDecoder (such as DnsNameResolver or custom DNS servers) is vulnerable.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "io.netty:netty-codec-dns"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.2.0.Final"
      }, {
        "fixed" : "4.2.16.Final"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.2.15.Final"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "io.netty:netty-codec-dns"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.1.136.Final"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.1.135.Final"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/security/advisories/GHSA-mfg7-5gfp-c4w3"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/pull/17063"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/pull/17065"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/netty/netty"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/releases/tag/netty-4.1.136.Final"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/releases/tag/netty-4.2.16.Final"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-772" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-24T16:52:50Z",
    "nvd_published_at" : null
  }
}