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CVE Record

CVE-2026-47691: Netty has Insufficient Bailiwick Validation for NS Records

Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, 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 (like `.co.uk`). In `io.netty.resolver.dns.DnsResolveContext.AuthoritativeNameServerList#add` method accepts any NS record from the AUTHORITY section as long as the record's name is a suffix of the questionName. Subsequently, the `handleWithAdditional` method caches the associated A records from the ADDITIONAL section directly into the `authoritativeDnsServerCache` under the parent domain's key. This bypasses standard bailiwick rules, where a server authoritative for a subdomain should not be trusted to provide authoritative records for its parent. The poisoned cache is then used for all future resolutions under the parent domain's key. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

HighCVSS 8.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Netty can trust DNS records from a subdomain too broadly, allowing cache poisoning for a parent domain. A successful attack could redirect future name resolutions made by affected applications, creating confidentiality and integrity risk. The issue is patched in Netty 4.1.135.Final and 4.2.15.Final.

Executive priority

Treat as a high-priority dependency update for internet-facing or DNS-dependent services using Netty. Business urgency is elevated because poisoned resolution can misdirect application traffic, but available evidence does not confirm active exploitation.

Technical view

Before 4.1.135.Final and 4.2.15.Final, Netty DnsResolveContext insufficiently enforced bailiwick rules for NS records. It could cache ADDITIONAL-section A records into authoritativeDnsServerCache under a parent-domain key, letting a subdomain authoritative server influence future resolutions for that parent domain.

Likely exposure

Exposure is most likely in Java applications or vendor products using vulnerable Netty resolver versions: below 4.1.135.Final, or 4.2.0.Final through before 4.2.15.Final.

Exploitation context

The provided sources describe a network attack with no privileges or user interaction, but high complexity. Evidence does not show CISA KEV listing or active exploitation. The attacker must control an authoritative name server for a subdomain and influence affected DNS resolution paths.

Researcher notes

Focus review on Netty DNS resolver usage and authoritativeDnsServerCache behavior. The key issue is accepting NS records based on suffix matching and caching associated A records for a broader parent-domain key, bypassing normal bailiwick trust boundaries.

Mitigation direction

  • Upgrade Netty to 4.1.135.Final or 4.2.15.Final.
  • Apply vendor packages or Red Hat errata where Netty is bundled.
  • Check dependency overrides so vulnerable transitive Netty versions are not retained.
  • Restart affected services after updating to rebuild in-process resolver cache state.

Validation and detection

  • Inventory applications and products that include io.netty resolver components.
  • Compare resolved Netty versions against the affected version ranges.
  • Confirm lockfiles, SBOMs, or runtime libraries show a patched Netty version.
  • Review vendor advisories for packaged Netty fixes and product-specific status.
Prepared
Confidence
high
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-345: Exact CWE lookup

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cwe · low confidence lookup

CWE-346: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2026-47691 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.7 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
12Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.7CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N2.25.8GitHub_M
8.7CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N2.25.8redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

8.7High
CVSS 3.1 vector shape for CVE-2026-47691Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPio.netty/netty-resolver-dns: Netty has Insufficient Bailiwick Validation for NS Records
other:Red Hat severity ratingcvssV3_1
  • 2026-06-12T16:02:45.855Z: Reported to Red Hat.
  • 2026-06-12T14:33:16.595Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
nettynetty>= 4.2.0.Final, < 4.2.15.Final, < 4.1.135.FinalListed
Weakness

CWE details

CWE-345CWE-346

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-345 · source CWE mapping

Insufficient Verification of Data Authenticity

Insufficient Verification of Data Authenticity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-346 · source CWE mapping

Origin Validation Error

Origin Validation Error represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs