CVE-2026-73508 is a medium-severity (CVSS 5.3) CWE-772 vulnerability in io.netty:netty-codec-dns. A fix is available for io.netty:netty-codec-dns — see the affected versions and patch details below.
Netty: Memory Leak in DNS Record Decoder via Malformed Domain Names
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-73508.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-73508 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
io.netty:netty-codec-dns☕io.netty:netty-codec-dnsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
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)invokesin.retainedDuplicate()or creates a new bufferoutwhen constructingDefaultDnsRawRecordio.netty.handler.codec.dns.DnsCodecUtil#decompressDomainNameallocates a newByteBufand passes it toencodeDomainName(). If the decompressed domain name contains a null byte (\0),encodeDomainName()throws anIllegalArgumentException, leaking the newly allocated buffer.
Impact
Resource Exhaustion. Any application utilizing Netty's DnsRecordDecoder (such as DnsNameResolver or custom DNS servers) is vulnerable.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.netty:netty-codec-dns | ≥ 4.2.0.Final&&< 4.2.16.Final | 4.2.16.Finalio.netty:netty-codec-dns:4.2.16.Final |
| ☕Maven | io.netty:netty-codec-dns | all versions | 4.1.136.Finalio.netty:netty-codec-dns:4.1.136.Final |
Affected Products
nettynettyDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec-dns, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.netty:netty-codec-dns to 4.2.16.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-73508 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This flaw is rated Important because the affected component fails to release allocated memory when it rejects a malformed domain name during DNS record decoding. An unauthenticated remote attacker who can send DNS traffic to an application using the affected DNS resolution functionality can incrementally exhaust…
Red Hat recommends upgrading to a fixed version as the primary remediation. Where an immediate upgrade is not possible, restrict network access so that only trusted DNS servers and trusted network peers can send DNS traffic to the affected application, using firewall or network policy rules to block or rate-limit DNS traffic from untrusted sources. This reduces exposure to the malformed DNS records that trigger the issue but does not fully eliminate it; upgrading remains the only complete fix.Source: Red Hat security advisory for CVE-2026-73508 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Data Grid 8.6.3 | netty-codec-dns | RHSA-2026:69296 |
| Red Hat JBoss Enterprise Application Platform 8.1 | netty-codec-dns | RHSA-2026:70277 |
| Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 10 | eap8-activemq-artemis-0:2.40.0-8.redhat_00024.1.el10eap | RHSA-2026:70230 |
| Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 | eap8-activemq-artemis-0:2.40.0-8.redhat_00024.1.el8eap | RHSA-2026:70228 |
| Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 | eap8-activemq-artemis-0:2.40.0-8.redhat_00024.1.el9eap | RHSA-2026:70229 |
| Red Hat OpenShift Dev Spaces 3.30 | devspaces/openvsx-rhel9:1789144269 | RHSA-2026:68754 |
Frequently Asked Questions
Is CVE-2026-73508 in your dependencies?
Find it across Maven, including transitive dependencies.