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CVE Record

CVE-2026-41292: Long list of incoming EDNS options degrades performance

NLnet Labs Unbound up to and including version 1.25.0 is vulnerable to a degradation of service attack related to parsing long lists of incoming EDNS options. An adversary sending queries with too many EDNS options can hold Unbound threads hostage while they are parsing and creating internal data structures for the options. Coordinated attacks can result in degradation and/or denial of service. Unbound 1.25.1 contains a patch with a fix to limit acceptable incoming EDNS options (100).

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Attackers who can send DNS queries to vulnerable Unbound resolvers can consume resolver capacity using unusually long EDNS option lists. Coordinated traffic may slow or deny DNS service, disrupting applications and users that depend on the resolver. The issue affects Unbound through 1.25.0; version 1.25.1 limits incoming EDNS options to 100.

Executive priority

Treat as a high-priority availability issue for business-critical DNS infrastructure. Expedite remediation for public or broadly accessible resolvers, then address constrained internal systems. The flaw does not claim data theft or modification, but DNS outages can create widespread application and workforce disruption.

Technical view

CVE-2026-41292 is an unauthenticated, network-reachable availability flaw in Unbound's EDNS option parsing. Excessive options keep processing threads occupied while internal option structures are created. Its CVSS 3.1 score is 7.5 with availability impact only: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Likely exposure

Unbound installations through version 1.25.0 are potentially exposed wherever untrusted clients can submit DNS queries. Public resolvers and internally reachable resolvers with broad client access warrant particular attention. The supplied structured affected-product entry conflicts with the narrative version range, so package-level vendor status should be confirmed.

Exploitation context

The attack requires sending crafted DNS queries containing excessive EDNS options; coordinated traffic can degrade or deny resolver service. No exploit procedure is provided. The bundle says this CVE is not in KEV and provides no evidence of active exploitation, public proof-of-concept availability, or observed attacks.

Researcher notes

The vendor description identifies Unbound through 1.25.0 as vulnerable and 1.25.1 as fixed by enforcing a 100-option limit. CWE mappings indicate asymmetric resource consumption and insufficient resource limits. The bundle's affected array lists version "0" with default status "unaffected," conflicting with the narrative; researchers should defer to the vendor advisory and applicable package advisories.

Mitigation direction

  • Upgrade Unbound to version 1.25.1 or a vendor-packaged build containing the CVE fix.
  • Review applicable distributor advisories and apply their supported security updates.
  • Prioritize resolvers reachable by untrusted or numerous clients.
  • Use existing network controls to restrict resolver access where operationally appropriate.

Validation and detection

  • Inventory Unbound versions and vendor package revisions across all DNS resolvers.
  • Confirm each installation is version 1.25.1 or has a documented vendor backport.
  • Identify which resolver interfaces accept queries from untrusted networks or broad internal populations.
  • Monitor resolver availability, latency, and thread saturation for unexplained degradation.
  • Verify vendor package status because the supplied structured affected-version data is inconsistent.
Prepared
Confidence
medium
Sources
5

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-1050: 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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cwe · low confidence lookup

CWE-407: 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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cwe · low confidence lookup

CWE-770: 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-2026-41292 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
7.5 (3.1)
Known Exploited
No
Published

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

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
12Timeline events
2ADP providers
10Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical 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
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP
6.6CVSS 4.0MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Red——NLnet Labs

Vulnerability scoring details

Base CVSS 4.0 score

6.6Medium
CVSS 4.0 vector shape for CVE-2026-41292Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Red

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

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

  1. Source timelineNLnet Labs

    Issue reported by N0zoM1z0

  2. Source timelineNLnet Labs

    NLnet Labs shares patch

  3. Source timelineNLnet Labs

    N0zoM1z0 verifies patch

  4. Source timelineNLnet Labs

    Issue also reported by Qifan Zhang

  5. Source timelineNLnet Labs

    NLnet Labs shares same patch

  6. Source timelineNLnet Labs

    Qifan Zhang verifies patch

  7. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  8. Source timelineNLnet Labs

    Fixes released with version 1.25.1

  9. ADP timelineredhat-SADP

    Made public.

  10. CVE publishedCVE Program

    The CVE record was published.

  11. ADP timelineredhat-SADP

    Reported to Red Hat.

  12. CVE updatedCVE Program

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

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPunbound: Unbound: Denial of Service via excessive EDNS options
other:Red Hat severity ratingcvssV3_1
  • 2026-05-20T10:00:54.433Z: Reported to Red Hat.
  • 2026-05-20T09:19:13.022Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
NLnet LabsUnbound0unaffected
Weakness

CWE details

CWE-1050CWE-407CWE-770

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

CWE-1050 · source CWE mapping

Excessive Platform Resource Consumption within a Loop

Excessive Platform Resource Consumption within a Loop represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-407 · source CWE mapping

Inefficient Algorithmic Complexity

Inefficient Algorithmic Complexity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-770 · source CWE mapping

Allocation of Resources Without Limits or Throttling

Allocation of Resources Without Limits or Throttling represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs