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CVE Record

CVE-2026-26017: CoreDNS ACL Bypass

CoreDNS is a DNS server that chains plugins. Prior to version 1.14.2, a logical vulnerability in CoreDNS allows DNS access controls to be bypassed due to the default execution order of plugins. Security plugins such as acl are evaluated before the rewrite plugin, resulting in a Time-of-Check Time-of-Use (TOCTOU) flaw. This issue has been patched in version 1.14.2.

HighCVSS 7.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CoreDNS versions before 1.14.2 can apply access-control decisions before later DNS rewrites change what is actually requested. An organization relying on CoreDNS ACLs may unintentionally allow access to DNS data that should have remained restricted.

Executive priority

Treat as a high-priority patching item for environments where CoreDNS enforces access to sensitive internal DNS data. Prioritize systems using ACLs and rewrites, then validate vendor-fixed packages across managed platforms.

Technical view

This is a CWE-367 time-of-check time-of-use flaw in CoreDNS plugin ordering. Security plugins such as acl can evaluate a query before rewrite changes it, allowing policy bypass. CVSS is 7.7 high: network attack vector, low complexity, low privileges, no user interaction, changed scope, and high confidentiality impact.

Likely exposure

Exposure is most likely where CoreDNS before 1.14.2 is deployed with ACL-style security controls and rewrite behavior. Kubernetes or internal DNS environments using CoreDNS should inventory versions and Corefile plugin configuration, but the bundle names only CoreDNS itself as affected.

Exploitation context

The source bundle does not show CISA KEV listing or cite active exploitation. The vulnerability is still important because DNS is often broadly reachable inside networks, and the CVSS vector indicates low attack complexity with no user interaction required.

Researcher notes

Key uncertainty is deployment-specific impact. The flaw depends on plugin composition and default execution order, so researchers should focus on configuration review, version validation, and vendor package mapping. Do not assume exploitation without additional evidence.

Mitigation direction

  • Upgrade CoreDNS to version 1.14.2 or later.
  • Review CoreDNS release notes and GitHub advisory for fixed behavior.
  • Check Red Hat errata if using Red Hat-packaged CoreDNS.
  • Audit Corefile usage of acl and rewrite together.
  • Apply vendor guidance rather than relying only on plugin reordering.

Validation and detection

  • Inventory all CoreDNS instances and package versions.
  • Identify Corefile configurations using acl or similar security plugins with rewrite.
  • Confirm deployed versions are 1.14.2 or vendor-fixed builds.
  • Review DNS logs for unexpected successful queries to ACL-protected zones.
  • Track remediation against Red Hat advisories where applicable.
Prepared
Confidence
high
Sources
6

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-367: 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-2026-26017 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
7.7 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/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
9Source links

SSVC decision data

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

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
7.7CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N3.14GitHub_M
7.7CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N3.14redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.7High
CVSS 3.1 vector shape for CVE-2026-26017Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/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-SADPgithub.com/coredns/coredns: CoreDNS: DNS access control bypass due to plugin execution order flaw
other:Red Hat severity ratingcvssV3_1
  • 2026-03-06T16:01:45.971Z: Reported to Red Hat.
  • 2026-03-06T15:36:15.655Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
corednscoredns< 1.14.2Listed
Weakness

CWE details

CWE-367

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

CWE-367 · source CWE mapping

Time-of-check Time-of-use (TOCTOU) Race Condition

Time-of-check Time-of-use (TOCTOU) Race Condition represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs