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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 flaw in dnsmasq DNSSEC validation can let an unauthenticated remote attacker crash the service using a crafted DNS packet. The expected impact is loss of DNS availability, not data theft or modification. Outages could disrupt name resolution and dependent network services.

Executive priority

Treat this as a high-priority availability risk. Rapidly identify dnsmasq in network infrastructure and embedded products, then patch critical or exposed resolvers first. The evidence does not support emergency incident declarations based on active exploitation, but DNS outages can have broad operational consequences.

Technical view

CVE-2026-4891 is a heap-based out-of-bounds read, classified as CWE-125, in dnsmasq DNSSEC validation. It is remotely reachable with low attack complexity and requires neither privileges nor user interaction. CVSS 3.1 scores it 7.5 because successful triggering can cause denial of service.

Likely exposure

Potentially exposed systems are those running an affected dnsmasq build and processing attacker-influenced DNS traffic through DNSSEC validation. The supplied affected-version value, "0," does not establish a reliable version range. Confirm exposure using dnsmasq and operating-system vendor advisories rather than that value alone.

Exploitation context

The bundle does not report CISA KEV listing or provide cited evidence of active exploitation. It supports remote, unauthenticated denial of service through a crafted DNS packet. Treat exploitation as technically plausible, but do not characterize it as observed in the wild without additional evidence.

Researcher notes

The central uncertainty is the affected-version range: the bundle reports only "0," which is not actionable. Researchers should rely on upstream and distribution advisories for vulnerable and fixed builds. Available evidence describes an out-of-bounds read and denial of service only; it does not substantiate code execution, confidentiality loss, or integrity impact.

Mitigation direction

  • Inventory dnsmasq installations, including embedded appliances, containers, routers, and bundled products.
  • Apply updates specifically identified by dnsmasq, operating-system vendors, or product maintainers for CVE-2026-4891.
  • Prioritize externally reachable or operationally critical DNS services.
  • Where updates are unavailable, review vendor guidance for supported temporary mitigations.
  • Maintain redundant DNS resolution to reduce outage impact during remediation.

Validation and detection

  • Record each deployed dnsmasq package version and its distributing vendor.
  • Compare versions against the dnsmasq CVE page and applicable vendor advisories.
  • Confirm updated packages explicitly address CVE-2026-4891.
  • Restart affected services when vendor instructions require it, then verify normal DNS resolution.
  • Monitor DNS service crashes, restarts, and anomalous malformed traffic.
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

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.

Open ATT&CK lookup
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.

Open ATT&CK lookup
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