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CVE Record

CVE-2026-4891: CVE-2026-4891

A heap-based out-of-bounds read vulnerability in the DNSSEC validation of dnsmasq allows remote attackers to cause a denial of service via a crafted DNS packet.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A remotely supplied DNS packet can trigger a memory read error while dnsmasq validates DNSSEC, causing the DNS service to fail. The documented impact is service disruption, not data theft or modification. Organizations relying on dnsmasq for name resolution should promptly identify affected deployments and follow applicable vendor guidance.

Executive priority

Treat this as a high-priority availability risk, especially where dnsmasq supports critical DNS, network access, or embedded services. Prioritize exposure discovery now, then patch according to vendor guidance. Escalate systems with DNSSEC enabled and broad exposure, while recognizing that active exploitation is not established by the supplied evidence.

Technical view

CVE-2026-4891 is a heap-based out-of-bounds read (CWE-125) in dnsmasq DNSSEC validation. It is rated CVSS 3.1 7.5: network-accessible, low complexity, requiring neither privileges nor user interaction. The assessed security impact is high availability loss, with no stated confidentiality or integrity impact.

Likely exposure

Exposure is most likely where dnsmasq performs DNSSEC validation and processes attacker-influenced DNS traffic. The supplied affected entry lists only version "0," so it does not establish a reliable affected-version range. Check each operating-system or bundled-product advisory for applicability.

Exploitation context

The source bundle does not identify CVE-2026-4891 as a CISA KEV vulnerability and provides no evidence of active exploitation. Remote denial of service is technically plausible under the stated low-complexity network attack conditions, but observed exploitation prevalence is unknown.

Researcher notes

The core weakness, attack vector, and denial-of-service impact are clearly described. However, the supplied version value "0" is inadequate for precise vulnerability matching, and no definitive upstream fixed version is stated in the bundle. Product-specific applicability should therefore be established from dnsmasq, CERT/CC, Red Hat, NixOS, or Pi-hole advisories.

Mitigation direction

  • Identify dnsmasq installations and products that bundle it.
  • Consult dnsmasq and relevant distributor advisories for confirmed affected versions.
  • Apply applicable vendor-provided security updates after normal change validation.
  • Restrict unnecessary DNS traffic paths while awaiting vendor-specific remediation guidance.

Validation and detection

  • Record dnsmasq package versions and their supplying vendors.
  • Determine whether DNSSEC validation is enabled on each deployment.
  • Compare versions against the applicable vendor advisory or erratum.
  • Confirm updated package versions and DNS service health after remediation.
  • Monitor DNS service restarts or unexplained availability failures.
Prepared
Confidence
medium
Sources
10

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-125: 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-2026-4891 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
5Timeline events
2ADP providers
15Source 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
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP
5.3CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N3.91.4CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-4891Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

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

    Reported to Red Hat.

  3. ADP timelineredhat-SADP

    Made public.

  4. CVE publishedCVE Program

    The CVE record was published.

  5. CVE updatedCVE Program

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

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
redhat-SADPdnsmasq: RRSIG rdlen underflow leading to heap OOB read
other:Red Hat severity ratingcvssV3_1
  • 2026-04-14T22:39:35.826Z: Reported to Red Hat.
  • 2026-05-09T00:00:00.000Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
dnsmasqdnsmasq0Listed
Weakness

CWE details

CWE-125

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

CWE-125 · source CWE mapping

Out-of-bounds Read

Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs