CVE-2026-47691 netty CVE debrief

Who should care

Defenders responsible for Netty deployments, DNS administrators, and security teams should assess exposure and apply patches. They should also review DNS resolution configurations to ensure proper validation of NS records and monitor for potential DNS cache poisoning attempts. Additionally, they should verify affected product deployments in managed environments and assign an owner for follow-up.

Why it matters

The vulnerability allows an attacker to poison the DNS cache for parent domains, potentially leading to DNS resolution issues and security risks. Defenders should prioritize verifying exposure and applying patches.

• Verify and apply patches for Netty versions before 4.1.135.Final and 4.2.15.Final to prevent DNS cache poisoning
• Review DNS resolution configurations to ensure proper validation of NS records
• Monitor for potential DNS cache poisoning attempts

Technical summary

Netty's `DnsResolveContext` insufficiently validates the bailiwick of NS records, enabling DNS Cache Poisoning. An attacker controlling an authoritative name server for a subdomain can poison the cache for parent domains. The issue is patched in Netty versions 4.1.135.Final and 4.2.15.Final. This vulnerability allows an attacker to manipulate DNS records, potentially leading to security risks and DNS resolution issues. Defenders should prioritize verifying exposure and applying patches for Netty versions before 4.1.135.Final and 4.2.15.Final.

Defensive priority

Defenders should prioritize verifying exposure and applying patches for Netty versions before 4.1.135.Final and 4.2.15.Final.

Recommended defensive actions

• Verify Netty version and apply patches for versions before 4.1.135.Final and 4.2.15.Final
• Review and update DNS resolution configurations to ensure proper validation of NS records
• Monitor for potential DNS cache poisoning attempts
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD entry provide details on the vulnerability and patches. Red Hat errata RHSA-2026:26017, RHSA-2026:26018, RHSA-2026:26586, RHSA-2026:34608, RHSA-2026:37390, RHSA-2026:41951, RHSA-2026:48151, RHSA-2026:49700, RHSA-2026:49701, RHSA-2026:50085, RHSA-2026:53644, RHSA-2026:53806, RHSA-2026:54435, RHSA-2026:62260, and RHSA-2026:65126 provide additional information on affected systems and patches.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.